msm: kgsl: Print the possible offending value on an opcode error

Snoop the internals of the CP and see the possibly invalid
opcode that triggered an opcode error.  This could be useful to
debug the situation that lead to the error.

Change-Id: Ic0dedbadb330e0764ac677c3d62cecc09464cef4
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>