msm: mdss: Add plane_count limit check for mdss_rotator buffer

For each input and output buffer given to mdss rotator, it is necessary
to check the range of the plane_count value against the MAX_PLANES
definition, in order to avoid any plane array out of bound access.

CRs-Fixed: 2028681
Change-Id: I117bf5daead17e5e97c62c6dc8e21d1fcc9d8e74
Signed-off-by: Benjamin Chan <bkchan@codeaurora.org>