soc: fsl: Correct MAINTAINERS database (QUICC ENGINE LIBRARY)

MAINTAINERS lacks of proper coverage for FSL headers. Fix it accordingly.

Fixes: 7aa1aa6e ("QE: Move QE from arch/powerpc to drivers/soc")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>