drm/i915/gem: remove inlines from i915_gem_execbuffer.c

Just let the compiler decide what's best. Turns out absolutely nothing
changes in the output with the inlines removed.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230921160637.3862597-1-jani.nikula@intel.com