soc: nordic: vpr: align ESF_SW_IRQ_SIZEOF when new exception debug is used

There is new exception debugging mechanism for RISC-V which needs
additional member in arch_esf structure. VPRs handle stacking
partially in hw so exact position of some stack members needs
to be at the end of arch_esf, so explicit padding is needed.
Aligned also ESF_SW_IRQ_SIZEOF when exception debug is used.

Signed-off-by: Łukasz Stępnicki <lukasz.stepnicki@nordicsemi.no>