intel: Rename genx keyword to gfxx in source files

Commands used to do the changes:
export SEARCH_PATH="src/intel src/gallium/drivers/iris src/mesa/drivers/dri/i965"
grep -E "gen[[:digit:]]+" -rIl $SEARCH_PATH | xargs sed -ie "s/gen\([[:digit:]]\+\)/gfx\1/g"

Exclude pack.h and xml changes in this patch:
grep -E "gfx[[:digit:]]+_pack\.h" -rIl $SEARCH_PATH | xargs sed -ie "s/gfx\([[:digit:]]\+_pack\.h\)/gen\1/g"
grep -E "gfx[[:digit:]]+\.xml" -rIl $SEARCH_PATH | xargs sed -ie "s/gfx\([[:digit:]]\+\.xml\)/gen\1/g"

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9936>

src/intel/compiler/brw_eu_validate.c

@@ -1628,7 +1628,7 @@ region_alignment_rules(const struct gen_device_info *devinfo,
     * destination must be an integer DWord, the hardware allows at least a
     * float destination type as well. We emit such instructions from
     *
-    *    fs_visitor::emit_interpolation_setup_gen6
+    *    fs_visitor::emit_interpolation_setup_gfx6
     *    fs_visitor::emit_fragcoord_interpolation
     *
     * and have for years with no ill effects.