m68k: Remove the BKL from sys_execve

This seems like a copy-and-paste from code that no-longer needs the BKL
Just remove it.

Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>