usb: pd: Don't wait to send outgoing requests in PE_SRC/SNK_READY

After handling incoming events in PE_SRC/SNK_READY, if the state
has not changed, allow pending outgoing requests (e.g. PR/DR
swap) to be sent without needing to wait for the next
invocation of the state machine.

Change-Id: I247e1093464e355ae7b6174ab06d41ce599d87e5
Signed-off-by: Jack Pham <jackp@codeaurora.org>