msm: kgsl: Correctly update fence_name for larger timestamp

Since 'timestamp' is of unsigned int type, for larger timestamp
the format specifier %d can show negative values. Fix this by
using %u format specifier for timestamp.

Change-Id: I621dfd4843099cb27436006500fe3342d1d5ddf4
Signed-off-by: Abhilash Kumar <krabhi@codeaurora.org>