irqchip: nvic: Fix offset for Interrupt Priority Offsets

According to ARM(v7M) ARM Interrupt Priority Offsets located at
0xE000E400-0xE000E5EC, while 0xE000E300-0xE000E33C covers read-only
Interrupt Active Bit Registers

Fixes: 292ec080 ("irqchip: Add support for ARMv7-M NVIC")
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211201110259.84857-1-vladimir.murzin@arm.com