Define AT91_USART0, 1, 2 so the selection of the UART for early kernel
messages works.
(See commit fa3218d859).
Replace AT91_SHDC with AT91_SHDWC to be consistent with other AT91 platforms.
Signed-off-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>