msm: kgsl: Detect and avoid malformed ioctl codes

Because we were using _IO_NR, one could construct a malformed ioctl
code that would avoid allocating memory yet go to a function that
expected that memory. Still use _IO_NR to index the array of ioctls,
but check that the full values match before jumping to the helper
function.

CRs-fixed: 385592
Change-Id: Ic0dedbaded469035bd0a2bb0f20fecb2a3045ca5
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>