powerpc/crypto: Add gitignore for generated P10 AES/GCM .S files

aesp10-ppc.S and ghashp10-ppc.S are autogenerated and not tracked by
git, so they should be ignored.  This is doing the same as the P8 files
in drivers/crypto/vmx/.gitignore but for the P10 files in
arch/powerpc/crypto.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230713042206.85669-1-ruscur@russell.cc