msm: mdp: Fix reserved field usage (fixes segmentation fault in recovery)

An earlier commit(ec5b2f)increased the number of reserved fields
in the kernel standard fb.h header changing the struct size.
This caused issues with userland applications using the corresponding
bionic header. This patch revert the earlier increas in size
and makes corresponding adjustments to the reserved field usage.
A follow up patch will remove usage of reserved fields entirely.

Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>