Having to call qe_ic_init() from platform-specific code makes it
awkward to allow building the QE drivers for ARM. It's also a needless
duplication of code, and slightly error-prone: Instead of the caller
needing to know the details of whether the QUICC Engine High and QUICC
Engine Low are actually the same interrupt (see e.g. the machine_is()
in mpc85xx_mds_qeic_init), just let the init function choose the
appropriate handlers after it has parsed the DT and figured it out. If
the two interrupts are distinct, use separate handlers, otherwise use
the handler which first checks the CHIVEC register (for the high
priority interrupts), then the CIVEC.

All existing callers pass 0 for flags, so continue to do that from the
new single caller. Later cleanups will remove that argument
from qe_ic_init and simplify the body, as well as make qe_ic_init into
a proper init function for an IRQCHIP_DECLARE, eliminating the need to
manually look up the fsl,qe-ic node.
Reviewed-by: Timur Tabi <timur@kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Li Yang <leoyang.li@nxp.com>