nvram: Drop the BKL from nvram_open()

It's safe to remove the BKL from nvram_open(): there's no open()
versus read() races: nvram_init() is very simple and race-free,
it registers the device then puts it into /proc - there's no
state init to race with.

Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <1255116426-7270-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>