drivers/tty/serial/crisv10.c: rename CPP identifier CONFIG_ETRAX_SERX_DTR_RI_DSR_CD_MIXED

The 'CONFIG_' prefix is reserved for Kconfig options in Make and CPP
syntax only.  Remove this prefix from the self-defined CPP identifier to
apply to this convention and make static analysis tools happy.

Signed-off-by: Valentin Rothberg <valentinrothberg@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>