drm/i915: fix register naming

This name was added with the whitelisting of registers for building up OA
configs. It is contained in a range gen8 whitelist :

   addr >= RPM_CONFIG0.reg && addr <= NOA_CONFIG(8).reg

Hence why the name isn't used anywhere.

v2: Fix register name again RPC->RCP (Matthew)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171110190845.32574-5-lionel.g.landwerlin@intel.com

drivers/gpu/drm/i915/i915_reg.h

@@ -1114,8 +1114,8 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 #define RPM_CONFIG0	    _MMIO(0x0D00)
 #define RPM_CONFIG1	    _MMIO(0x0D04)
 
-/* RPC unit config (Gen8+) */
-#define RPM_CONFIG	    _MMIO(0x0D08)
+/* RCP unit config (Gen8+) */
+#define RCP_CONFIG	    _MMIO(0x0D08)
 
 /* NOA (HSW) */
 #define HSW_MBVID2_NOA0		_MMIO(0x9E80)