drm/i915: remove superfluous string helper include

Remove the duplicate and incorrect (uses "" instead of <>)
linux/string_helpers.h include.

Fixes: cc1338f2 ("drm/i915/xehp: Update topology dumps for Xe_HP")
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220425154754.990815-1-jani.nikula@intel.com

drivers/gpu/drm/i915/gt/intel_sseu.c

@@ -10,8 +10,6 @@
 #include "intel_gt_regs.h"
 #include "intel_sseu.h"
 
-#include "linux/string_helpers.h"
-
 void intel_sseu_set_info(struct sseu_dev_info *sseu, u8 max_slices,
 			 u8 max_subslices, u8 max_eus_per_subslice)
 {