usb: typec: tcpci_rt1711h: Unmask alert interrupts to fix functionality

During probe, the TCPC alert interrupts are getting masked to
avoid unwanted interrupts during chip setup: this is ok to do
but there is no unmasking happening at any later time, which
means that the chip will not raise any interrupt, essentially
making it not functional as, while internally it does perform
all of the intended functions, it won't signal anything to the
outside.

Unmask the alert interrupts to fix functionality.

Fixes: ce08eaeb ("staging: typec: rt1711h typec chip driver")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>