By the time we're disabling the endpoint, HW
could already have posted more events to our
event buffer. In that case, we will receive
endpoint events for a disabled endpoint.

In order to protect ourselves from that situation,
we simply ignore endpoint interrupts whenever
the endpoint is disabled.
Tested-by: NPratyush Anand <pratyush.anand@st.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>