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: NBen Dooks <ben.dooks@codethink.co.uk>
Link: https://lore.kernel.org/r/20191009135356.11180-1-ben.dooks@codethink.co.ukSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>