staging: iio: ad5933: fix sparse warnings

Fix the following sparse warnings:

  CHECK   drivers/staging/iio/impedance-analyzer/ad5933.c
drivers/staging/iio/impedance-analyzer/ad5933.c:241:17: warning:
incorrect type in assignment (different base types)
drivers/staging/iio/impedance-analyzer/ad5933.c:241:17:    expected
unsigned int [unsigned] [usertype] d32
drivers/staging/iio/impedance-analyzer/ad5933.c:241:17:    got
restricted __be32 [usertype] <noident>
drivers/staging/iio/impedance-analyzer/ad5933.c:263:13: warning:
incorrect type in assignment (different base types)
drivers/staging/iio/impedance-analyzer/ad5933.c:263:13:    expected
unsigned short [unsigned] dat
drivers/staging/iio/impedance-analyzer/ad5933.c:263:13:    got
restricted __be16 [usertype] <noident>
drivers/staging/iio/impedance-analyzer/ad5933.c:271:13: warning:
incorrect type in assignment (different base types)
drivers/staging/iio/impedance-analyzer/ad5933.c:271:13:    expected
unsigned short [unsigned] [addressable] dat
drivers/staging/iio/impedance-analyzer/ad5933.c:271:13:    got
restricted __be16 [usertype] <noident>
drivers/staging/iio/impedance-analyzer/ad5933.c:310:19: warning: cast to
restricted __be32
drivers/staging/iio/impedance-analyzer/ad5933.c:310:19: warning: cast to
restricted __be32
drivers/staging/iio/impedance-analyzer/ad5933.c:310:19: warning: cast to
restricted __be32
drivers/staging/iio/impedance-analyzer/ad5933.c:310:19: warning: cast to
restricted __be32
drivers/staging/iio/impedance-analyzer/ad5933.c:310:19: warning: cast to
restricted __be32
drivers/staging/iio/impedance-analyzer/ad5933.c:310:19: warning: cast to
restricted __be32
drivers/staging/iio/impedance-analyzer/ad5933.c:446:21: warning:
incorrect type in assignment (different base types)
drivers/staging/iio/impedance-analyzer/ad5933.c:446:21:    expected
unsigned short [unsigned] dat
drivers/staging/iio/impedance-analyzer/ad5933.c:446:21:    got
restricted __be16 [usertype] <noident>
drivers/staging/iio/impedance-analyzer/ad5933.c:454:21: warning:
incorrect type in assignment (different base types)
drivers/staging/iio/impedance-analyzer/ad5933.c:454:21:    expected
unsigned short [unsigned] [addressable] dat
drivers/staging/iio/impedance-analyzer/ad5933.c:454:21:    got
restricted __be16 [usertype] <noident>
drivers/staging/iio/impedance-analyzer/ad5933.c:548:23: warning: cast to
restricted __be16
drivers/staging/iio/impedance-analyzer/ad5933.c:548:23: warning: cast to
restricted __be16
drivers/staging/iio/impedance-analyzer/ad5933.c:548:23: warning: cast to
restricted __be16
drivers/staging/iio/impedance-analyzer/ad5933.c:548:23: warning: cast to
restricted __be16

Signed-off-by: Teodora Baluta <teodora.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>