syscall: fix arm build
syscall: fix arm build

Rename Seek to seek in asm file, was overlooked in CL 99320043.

LGTM=bradfitz, r
R=r, rsc, bradfitz
CC=golang-codereviews
https://codereview.appspot.com/99320044

pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,tv42/old-go