drivers: input: sbus: Fix race and infinite loop

Under certain conditions report_lock could already be used by the irq
before it was initialized, now we ensure we enable irq after report_lock
is initialized.

Furthermore in some conditions data->xfer_bytes could be equal
SBUS_FRAME_LEN resulting in a infinite loop doing zero reads when
fifo is still holding new bytes

Signed-off-by: Peter van der Perk <peter.vanderperk@nxp.com>