powerpc/tqm85xx: add a quirk for ti1520 PCMCIA bridge

By default ti1520 bridge expects an input clock on CLOCK pin (to control
power chip). However on this boards CLOCK should be generated by PCI1520
itself. Add a quirk that enables internal 16 KHz clock generation on
this pin.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>