soc: fsl: qe: fix static checker warning

The patch be7ecbd2: "soc: fsl: qe: convert QE interrupt
controller to platform_device" from Aug 3, 2021, leads to the
following static checker warning:

	drivers/soc/fsl/qe/qe_ic.c:438 qe_ic_init()
	warn: unsigned 'qe_ic->virq_low' is never less than zero.

In old variant irq_of_parse_and_map() returns zero if failed so
unsigned int for virq_high/virq_low was ok.
In new variant platform_get_irq() returns negative error codes
if failed so we need to use int for virq_high/virq_low.

Also simplify high_handler checking and remove the curly braces
to make checkpatch happy.

Fixes: be7ecbd2 ("soc: fsl: qe: convert QE interrupt controller to platform_device")
Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>