rust: build: Fix grep warning
Fix grep warning during the build, with GNU grep 3.8
with the following command
`grep -v '^\#\|^$$' rust/bindgen_parameters`
I see the following warning
```
grep: warning: stray \ before #
--opaque-type xregs_state
--opaque-type desc_struct
--opaque-type arch_lbr_state
--opaque-type local_apic
--opaque-type x86_msi_data
--opaque-type x86_msi_addr_lo
--opaque-type kunit_try_catch
--opaque-type spinlock
--no-doc-comments
```
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Tested-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>