serial: sc16is7xx: rename LCR macros to better reflect usage

serial: sc16is7xx: rename LCR macros to better reflect usage

There is no reference to CONF_MODE_A or CONF_MODE_B in the manufacturer's
datasheet.

Rename register set configuration macros for the LCR register, to better
show their intended usage to select either the Special register set, or the
Enhanced register set.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://patch.msgid.link/20251027142957.1032073-2-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>