package/gcc: fix check-package warnings in patches

package/gcc/11.3.0/0005-rs6000-Improve-.machine.patch:4: generate your patches with 'git format-patch -N'
package/gcc/11.3.0/0006-rs6000-Do-not-use-rs6000_cpu-for-.machine-ppc-and-pp.patch:4: generate your patches with 'git format-patch -N'

Signed-off-by: Arnout Vandecappelle <arnout@mind.be>