msm: kgsl: add IOCTL_KGSL_GPUMEM_ALLOC_ID

Previously, the gpu address has been used to uniquely
identify each memory allocation. Upcoming patches will
introduce cases where an allocation does not always
have a gpu address, so an additional id is needed.

IOCTL_KGSL_GPUMEM_ALLOC_ID allocates pages and returns
an id.

IOCTL_KGSL_GPUMEM_FREE_ID frees an id. KGSL_SHAREDMEM_FREE
can still be used to free by GPU address, if it exists.

The id can also be passed to mmap(), shifted left by
PAGE_SIZE to get a CPU mapping for the buffer.

IOCTL_KGSL_GPUMEM_ALLOC_GET_INFO can be called to retrieve
the id and other information about the buffer.

Change-Id: I4b45f0660cb9d4a5fb1323ccc6c4aa360791c1ec
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>