powerpc/fsl_pci: fix 64 bit pci size issue

The size might be 64 bit, so use ilog2() instead of __ilog2() or
__ilog2_u64().

ilog2() can select 32bit or 64bit function automatically.

Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>