powerpc/32: Interchange r10 and r12 in SYSCALL_ENTRY on non booke

To better match booke version of SYSCALL_ENTRY macro, interchange
r10 and r12 in the non booke version.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5ab3a517bc883a2fc905fb2cb5ee9344f37b2cfa.1622818435.git.christophe.leroy@csgroup.eu