msm: kgsl: Fix the KGSL driver to compile when CONFIG_DEBUG_FS=n

Fix a compilation error when CONFIG_DEBUG_FS is disabled. Add an
initialization flag to the process struct rather than rely on a
pointer to the debugfs node which will always be NULL if debugfs
is not available.

CRs-fixed: 542231
Change-Id: Ic0dedbadf0241fd476e56d6e116a811697b38190
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>