drivers/rtc/rtc-pl031.c: enable clock on all ST variants

drivers/rtc/rtc-pl031.c: enable clock on all ST variants

BugLink: http://bugs.launchpad.net/bugs/987337

commit 2f3972168353d355854d6381f1f360ce83b723e5 upstream.

The ST variants of the PL031 all require bit 26 in the control register
to be set before they work properly.  Discovered this when testing on
the Nomadik board where it would suprisingly just stand still.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Mian Yousaf Kaukab <mian.yousaf.kaukab@stericsson.com>
Cc: Alessandro Rubini <rubini@unipv.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>