uboot-phytec

serial: bcm283x_mu: make pending values more explicit

dm_serial_ops.pending should return the number of characters, not just a
valid C Boolean integer value. The existing code does already does this,
but only as an accident since BCM283X_MU_LSR_RX_READY happens to be
BIT(0). Enhance the code to be more explicit about the values it returns.

Suggested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>