build: fix issue with static interrupts on ARC/ARM

Static interrupts rely on a trick where the _sw_isr_table array
is declared with each element in a different .gnu.linkonce
section, initially pointing to the spurious IRQ handler.

When drivers or apps declare their own interrupts, they override
the element with their own containing the real ISR and parameter.

However, this only works if the initial declaration of the
_sw_isr_table array with the spurious handlers is linked last.
App-specific code was being linked later than the core code,
causing static interrupts declared in apps not to be installed
correctly.

If the _sw_isr_table is moved from SOC-specific code to core arch
code, interrupts configured under soc/ should still also work.

Change-Id: Iec7df47386dfbbf2956a807da27dc8aa6e01b268
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>