rust: ignore -fzero-call-used-regs=% from GCC 11

GCC 11 introduces this flag which the kernel uses and thus `bindgen`
complains, so add it to the skip list.

In the CI, so far, we are using the GCCs provided by Ubuntu 20.04,
which are prior to GCC 11.

I checked that in an alternative CI with GCC 11.2 (from a Docker Ubuntu
21.10 image) this commit fixes the problem.

Link: https://lore.kernel.org/lkml/202201310402.vCWP8CUS-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

rust/Makefile

@@ -204,6 +204,7 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
 	-femit-struct-debug-baseonly -fno-ipa-cp-clone -fno-ipa-sra \
 	-fno-partial-inlining -fplugin-arg-arm_ssp_per_task_plugin-% \
 	-fno-reorder-blocks -fno-allow-store-data-races -fasan-shadow-offset=% \
+	-fzero-call-used-regs=% \
 	-Wno-packed-not-aligned -Wno-format-truncation -Wno-format-overflow \
 	-Wno-stringop-truncation -Wno-unused-but-set-variable \
 	-Wno-stringop-overflow -Wno-restrict -Wno-maybe-uninitialized \