Add support for mark/space parity in TTY for UART

[smaryus_gmail.com]

Summary

Add support to configure mark/space parity for uart tty.

This is blocked by https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=237576 To work parity errors must work correctly in UART.

Test Plan

1. Build kernel and configure UART like into the sample code.

struct termios tio;
 tcgetattr(fd, &tio);
 cfmakeraw(&tio);
 tio.c_cflag |= CMSPAR;
 tio.c_cflag |= PARODD;         // select space parity so that only address byte causes error
 tio.c_cflag |= PARENB;         // enable parity generation
 tio.c_cflag |= CSIZE | CS8;
 tio.c_iflag |= INPCK;          // enable parity checking
 tio.c_iflag |= PARMRK;         // enable in-band marking 
 tio.c_iflag &= ~IGNPAR;         // make sure input parity errors are not ignored

tcsetattr(fd, TCSANOW, &tio);

2. Send data on UART with the mark space. This will generate an parity error inside UART and TTY will send 0xff + 0x00 + the_received_byte.