phy: phy-brcm-usb: Utilize platform_get_irq_byname_optional()

The wake-up interrupt lines are entirely optional, avoid printing
messages that interrupts were not found by switching to the _optional
variant.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Justin Chen <justinpopo6@gmail.com>
Link: https://lore.kernel.org/r/20221026224450.2958762-1-f.fainelli@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>