msm: kgsl: Move the pdata structure from the public API header

The pdata structure and associated structs have no business being
in msm_kgsl.h.  Move them to include/mach/kgsl.h where they can
thrive in a non-userspace facing environment.

Change-Id: Ic0dedbadfe0d3d7d44f50c8a9a7f4cc59057d44b
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>