ppc: fix comment typo singal -> signal

The patches below fixes a typo "singal" to "signal".

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

arch/powerpc/platforms/85xx/mpc85xx_mds.c

@@ -309,7 +309,7 @@ static void __init mpc85xx_mds_qe_init(void)
 			/* P1021 has pins muxed for QE and other functions. To
 			 * enable QE UEC mode, we need to set bit QE0 for UCC1
 			 * in Eth mode, QE0 and QE3 for UCC5 in Eth mode, QE9
-			 * and QE12 for QE MII management singals in PMUXCR
+			 * and QE12 for QE MII management signals in PMUXCR
 			 * register.
 			 */
 				setbits32(pmuxcr, MPC85xx_PMUXCR_QE0 |