powerpc: Move the setting of rflags out of loop in __hash_page_huge

It seems that new_pte and rflags don't get changed in the repeating loop, so
move their assignment out of the loop.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>