[POWERPC] Fix compile error if CONFIG_STX_GP3 is defined

cpmux is need in all cases, having wrapped by the ifndef CONFIG_STX_GP3
was causing a compile error.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

drivers/serial/cpm_uart/cpm_uart_cpm2.c

@@ -165,9 +165,9 @@ void scc2_lineif(struct uart_cpm_port *pinfo)
 	 * really has to get out of the driver so boards can
 	 * be supported in a sane fashion.
 	 */
+	volatile cpmux_t *cpmux = cpm2_map(im_cpmux);
 #ifndef CONFIG_STX_GP3
 	volatile iop_cpm2_t *io = cpm2_map(im_ioport);
-	volatile cpmux_t *cpmux = cpm2_map(im_cpmux);
 
 	io->iop_pparb |= 0x008b0000;
 	io->iop_pdirb |= 0x00880000;