[MTD] Fix ixp4xx partition parsing.

If the amount of flash is not divisible by 2 then the mask in
parse_mtd_partitions would fail to work as designed.  Passing in the base
address corrects this problem.

Signed-off-by: Brian Walsh <brian@walsh.ws>
Cc: Deepak Sanexa <dsanexa@mvista.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>