[ARM] 5052/1: export clock functions for the at91x40

Export the AT91 clock functions for the AT91X40. Some external code common
to all AT91 family parts relys on this, like the gpio and serial support.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>