drm/xe: Remove unused FF_SLICE_CS_CHICKEN2

Commit e89f4967 ("drm/xe: Drop WA 16015675438") removed the only
user of that register and should have removed it. Remove it now.
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240306192128.1895603-1-lucas.demarchi@intel.comSigned-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/regs/xe_engine_regs.h

@@ -104,9 +104,6 @@
 #define FF_SLICE_CS_CHICKEN1(base)		XE_REG((base) + 0xe0, XE_REG_OPTION_MASKED)
 #define   FFSC_PERCTX_PREEMPT_CTRL		REG_BIT(14)
 
-#define FF_SLICE_CS_CHICKEN2(base)		XE_REG((base) + 0xe4, XE_REG_OPTION_MASKED)
-#define   PERF_FIX_BALANCING_CFE_DISABLE	REG_BIT(15)
-
 #define CS_DEBUG_MODE1(base)			XE_REG((base) + 0xec, XE_REG_OPTION_MASKED)
 #define   FF_DOP_CLOCK_GATE_DISABLE		REG_BIT(1)
 #define   REPLAY_MODE_GRANULARITY		REG_BIT(0)