Remove wrong fifo size definition for some AT91 products.

Due to a misunderstanding of some AT91 datasheets, a fifo size of 2048
(words) has been introduced by mistake.  In fact, all products (AT91/AT32)
are sharing the same fifo size of 512 words.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Andrew Victor <avictor.za@gmail.com>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>