[POWERPC] CPM_UART: Removed __init from cpm_uart_init_portdesc to fix warning

cpm_uart_init_portdesc is referenced from non-init code and thus we were
getting the following warning:

WARNING: drivers/built-in.o - Section mismatch: reference to .init.text:cpm_uart_init_portdesc from .text between 'cpm_uart_init' (at offset 0x18020) and 'cpm_uart_drv_remove'

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>