AT91: Enable PLLB for USB

At least some (old ?) versions of the AT91Bootstrap do not set up the
PLLB correctly to 48 MHz in order to make USB host function correctly.

This patch sets up the PLLB to the same values Linux uses, and makes USB
work ok on the following CPUs:
	- AT91CAP9
	- AT91SAM9260
	- AT91SAM9263

This patch also defines CONFIG_USB_STORAGE and CONFIG_CMD_FAT for all
the relevant AT91CAP9/AT91SAM9 atmel boards.

Signed-off-by: Stelian Pop <stelian@popies.net>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>