drm/xe/guc: Fix sizeof(32) typo

drm/xe/guc: Fix sizeof(32) typo

A small typo leads to the following static code checker warning:

	drivers/gpu/drm/xe/xe_guc_buf.c:81 xe_guc_buf_reserve()
	warn: sizeof(NUMBER)?

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/intel-xe/0d5bcbf1-79f9-4a10-a221-ddbaec9f6122@stanley.mountain/
Fixes: 696bfdf273ea ("drm/xe/guc: Introduce the GuC Buffer Cache")
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250121094832.588-1-michal.wajdeczko@intel.com