[nrf fromlist] soc: nrf54h: use word accesses to SPI_DW peripheral

The nRF54H20 EXMIF peripheral requires word accesses. Doing accesses of
byte or half-word sizes results in bus fault.

Upstream PR: zephyrproject-rtos/zephyr#72497

Signed-off-by: Rafał Kuźnia <rafal.kuznia@nordicsemi.no>

soc/nordic/nrf54h/Kconfig.defconfig

@@ -36,4 +36,7 @@ endif # RISCV
 config SPI_DW_HSSI
 	default y if SPI_DW
 
+config SPI_DW_ACCESS_WORD_ONLY
+	default y if SPI_DW
+
 endif # SOC_SERIES_NRF54HX