tty/serial: at91: remove bunch of macros to access UART registers

This patch replaces the UART_PUT_*, resp. UART_GET_*, macros by
atmel_uart_writel(), resp. atmel_uart_readl(), inline function calls.
Signed-off-by: NCyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>