drm/i915: Remove duplicate inline specifier on write_pte

drm/i915: Remove duplicate inline specifier on write_pte

When building with clang:

 drivers/gpu/drm/i915/gt/gen8_ppgtt.c:392:24: warning: duplicate
 'inline' declaration specifier [-Wduplicate-decl-specifier]
 declaration specifier [-Wduplicate-decl-specifier]
 static __always_inline inline void
                        ^
 include/linux/compiler_types.h:138:16: note: expanded from macro
 'inline'
 #define inline inline __gnu_inline __inline_maybe_unused notrace
                ^
 1 warning generated.

__always_inline is defined as 'inline __attribute__((__always_inline))'
so we do not need to specify it twice.

Fixes: 84eac0c65940 ("drm/i915/gt: Force pte cacheline to main memory")
Link: https://github.com/ClangBuiltLinux/linux/issues/1024
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200513182340.3968668-1-natechancellor@gmail.com