tty: serial: meson: remove duplicate "clear error" bit definition

The "clear error" bit in the AML_UART_CONTROL register is defined twice.
Remove the AML_UART_CLR_ERR definition and replace it with
AML_UART_CLEAR_ERR.
AML_UART_CLEAR_ERR was chosen to be kept since the datasheet's
description for this bit is "Clear Error" (so developer's don't have to
translate this to "CLR_ERR").
No functional changes intended.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>