msm: camera: Fix inconsistent behavior of VFE_READ_DMI_64BIT

VFE_READ_DMI_64BIT behavior is not consistent with VFE_WRITE_DMI_64BIT
The latter accepts array of 64bit values as an input to write to HW,
while the former reads the data from hw into two separate arrays - one
for the hi words and one for the low words.
This patch makes read consistent with write - it will read data in one
64bit array.

Change-Id: Iac8b46ca0893705b0e4b1713e78225dc3eb430ad
Signed-off-by: Petar Sivenov <psiven@codeaurora.org>