powerpc: Refactor board check for PCI quirks on FSL boards with uli1575

Refactor the check to determine if the quirk is applicable to the boards
into one inline function so we only have to change one place to add more
boards that the quirks might be applicable to.

Also removed a warning related to unused temp variable.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>