serial: liteuart: use bit number macros

Replace magic bit constants (e.g., 1, 2, 4) with BIT(x) expressions.

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20221123130500.1030189-3-gsomlo@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>