soc: nordic: vpr: remove enabling MSTATUS.MIE in boot time

Interrupts should not be enabled this early in boot time.
Driver initializations expect IRQs not to arrive when
setting up HW.
Remove enabling `MSTATUS.MIE` in `__start`.
It will be enabled when main thread is switched to,
as threads by default start with enabled `MSTATUS.MIE`.

Signed-off-by: Marcin Szymczyk <marcin.szymczyk@nordicsemi.no>

soc/nordic/common/vpr/vector.S

@@ -20,9 +20,5 @@ SECTION_FUNC(vectors, __start)
 	la t0, _irq_vector_table
 	csrw 0x307, t0
 
-	/* Enable mstatus.mie */
-	li t0, 0x1888
-	csrw mstatus, t0
-
 	/* Call into Zephyr initialization. */
 	tail __initialize