hwmon: (occ) OCC sensors aren't arch-specific

Commit c112d758

 ("hwmon: OCC drivers are ARM-only") made the OCC
sensor drivers not selectable on powerpc64:

  These drivers are for a BMC inside PowerPC servers. The BMC runs on
  ARM hardware, so only propose the drivers on this architecture, unless
  build-testing.

... but we now have a powerpc64 BMC (still for a powerpc64 host), so
drop the `depends on` that excludes building for this platform.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Acked-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20221024081527.3842565-1-jk@codeconstruct.com.au
Signed-off-by: Guenter Roeck <linux@roeck-us.net>