usb: chipidea: imx: fix a typo for imx6sx
usb: chipidea: imx: fix a typo for imx6sx

Use imx6sx instead of imx6sl's platform flags for imx6sx.

Fixes: e14db48dfcf3 ("usb: chipidea: imx: add runtime power management support")
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org> # v4.1+
Signed-off-by: Li Jun <6ec34a90a24ebc739c91c1430f6b3f83b3480552@freescale.com>
Signed-off-by: Peter Chen <c01a8c815a4ad165fff2d1c0d35ddf5b16bd3d7b@freescale.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs