[ARM] 4154/1: AT91: Clock update

Unconditionally disabling the PCKs (Programmable Clocks) is not a good
idea as it breaks boards that depend on those clocks being enabled by
bootloaders.
Therefore only disable unused clocks late in the init process, giving
the board init code the chance to claim the clock.

Patch from Steven Scholz.

Since the HCK clocks on SAM9261 are already being registered as a
independent clocks, we don't need the special case for HCK0 on the
SAM9261.  Platform-init code and drivers should use the clock API to
enable/disable the clock.

Patch from Nicolas Ferre.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>