xtensa: nxp_adsp: common: Remove soc.c

The soc.c interrupt-related definitions are supposed to
provide support for multi-level interrupts. At the moment,
the way the functions work is they only process the LEVEL 1
interrupt from the encoded INTID and treats the provided INTID
as if it were simply a LEVEL 1 interrupt, which is wrong. Another
issue with soc.c is the fact that the definitions from it clash
with the ones provided by the IRQSTEER driver. To fix this, remove
the soc.c file altogether and change the corresponding CMakeLists.txt
to only contain the necessary statements.

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>