msm: kgsl: Avoid mixing signed and unsigned ints in kgsl_sysfs_store

kstrtou32 returns negative on error or 0 on success.  kgsl_sysfs_store
then proceeded to either return the negative value or the unsigned int
'count'.  Furthermore it compared the return value of kgsl_sysfs_store
against an unsigned int so streams were crossed everywhere.

Remove the uneeded count paramater, return 0 or negative from
kgsl_sysfs_store and handle it appropriately.

Change-Id: Ic0dedbad40e0b914cd06f5a9003a289d3307a14e
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>