Add ADDRB from Linux 6.0 to bits/termios-c_cflag.h

Linux 6.0 adds a constant ADDRB, a termios c_cflag bit, to its
include/uapi/asm-generic/termbits-common.h.

Add it accordingly to glibc's bits/termios-c_cflag.h headers.  As
other constants in these headers are generally in octal, I converted
the value to octal to match.  As ADDRB isn't in a POSIX-reserved
namespace, I made it conditional on __USE_MISC.

Tested for x86_64.