imx6: clock: typo fix

Typo fix, "PPL2 -> PLL2"

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>

arch/arm/cpu/armv7/mx6/clock.c

@@ -281,7 +281,7 @@ static u32 mxc_get_pll_pfd(enum pll_clocks pll, int pfd_num)
 	case PLL_BUS:
 		if (!is_mx6ul()) {
 			if (pfd_num == 3) {
-				/* No PFD3 on PPL2 */
+				/* No PFD3 on PLL2 */
 				return 0;
 			}
 		}