serial: sirf: make register info static

The sirfsoc_usp and sirfsoc_uart objects are not
used outside of the drivers/tty/serial/sirfsoc_uart.o
so make them static. Fixes following sparse warnings:

drivers/tty/serial/sirfsoc_uart.h:123:30: warning: symbol 'sirfsoc_usp' was not declared. Should it be static?
drivers/tty/serial/sirfsoc_uart.h:189:30: warning: symbol 'sirfsoc_uart' was not declared. Should it be static?
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Link: https://lore.kernel.org/r/20191009135356.11180-1-ben.dooks@codethink.co.ukSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sirfsoc_uart.h

@@ -120,7 +120,8 @@ static u32 uart_usp_ff_empty_mask(struct uart_port *port)
 	empty_bit = ilog2(port->fifosize) + 1;
 	return (1 << empty_bit);
 }
-struct sirfsoc_uart_register sirfsoc_usp = {
+
+static struct sirfsoc_uart_register sirfsoc_usp = {
 	.uart_reg = {
 		.sirfsoc_mode1		= 0x0000,
 		.sirfsoc_mode2		= 0x0004,
@@ -186,7 +187,7 @@ struct sirfsoc_uart_register sirfsoc_usp = {
 	},
 };
 
-struct sirfsoc_uart_register sirfsoc_uart = {
+static struct sirfsoc_uart_register sirfsoc_uart = {
 	.uart_reg = {
 		.sirfsoc_line_ctrl	= 0x0040,
 		.sirfsoc_tx_rx_en	= 0x004c,