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>

CVE-2012-4222:
Several integer overflows in the processing of DIAG ioctl system call
parameters allow a locally installed application to conduct denial of
service (DoS) attacks or possibly execute arbitrary code in kernel
context.
https://www.codeaurora.org/projects/security-advisories/multiple-issues-diagkgsl-system-call-handling-cve-2012-4220-cve-2012