iio: hmc5843: Swap suspend and resume implementations

Swap implementations of hmc5843_common_suspend and
hmc5843_common_resume functions for they have been
inversed. Device should go on SLEEP mode on suspend
and on CONTINUOUS mode on resume.

Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>