[dev.power64] syscall: fix power64 page size
[dev.power64] syscall: fix power64 page size

LGTM=minux
R=minux
CC=golang-codereviews
https://codereview.appspot.com/128260043

d0f/go-zh,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,d0f/go-zh,d0f/go-zh,d0f/go-zh,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,bryanxu/go-zh,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,d0f/go-zh,d0f/go-zh,webfd/go-zh,webfd/go-zh,bryanxu/go-zh,webfd/go-zh,d0f/go-zh