blackfin: Remove the BKL from sys_execve

This looks like a cut-and-paste job. For example, compare this
function to sys_execve in arch/x86/kernel/process_64.c and it is
almost line by line the same, except the one in x86 nolonger has the
big kernel lock. All of the functions called between the lock are
generic and not specific to blackfin - thus, I believe it is safe to
remove the bkl here.

Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
LKML-Reference: <alpine.LFD.2.00.0910130007240.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>