drivers: video: msm: drop some unused variables

Just dropping a couple of warnings from this driver,

linux-2.6/drivers/video/msm/mdp.c: In function 'get_img':
linux-2.6/drivers/video/msm/mdp.c:261: warning: unused variable 'vstart'

linux-2.6/drivers/video/msm/mddi.c: In function 'mddi_handle_rev_data_avail':
linux-2.6/drivers/video/msm/mddi.c:193: warning: unused variable 'i'
linux-2.6/drivers/video/msm/mddi.c:190: warning: unused variable 'rev'

Signed-off-by: Daniel Walker <dwalker@codeaurora.org>