serial: sirf: use dynamic method allocate uart structure

In different platform of SiRF SoCs, there is no same uart and usp-uart
numbers, it is not convenient to use hard-coded ports array and port
lines.

here we drop the hard-coded ports table , and drop "cell-index". then
move to use alias id to get line.

for example:
	aliases {
		serial0 = &uart0;
		serial1 = &uart1;
		serial2 = &uart2;
		serial3 = &uart3;
		serial4 = &uart4;
		serial5 = &uart5;
		serial6 = &uart6;
		serial9 = &usp2;
	};

at the same, enlarge the max port number according to the chip with the most
UART.

Signed-off-by: Qipan Li <Qipan.Li@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>