mn10300: Remove the BKL from sys_execve

This looks like a cut-and-paste from functionality that no-longer
needs the bkl Just remove it. Also, rewrite slightly so that it looks
closer to sys_execve on other architectures.

Signed-off-by: John Kacur <jkacur@redhat.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
LKML-Reference: <alpine.LFD.2.00.0910130016540.3658@localhost.localdomain>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>