CONFIG_SERIAL_TERMIOS only decide whether to support c_cflag field since
many terminal application need the first three fields to work correctly.
For more information please reference:
https://www.mail-archive.com/dev@nuttx.apache.org/msg09321.html
before this change(olimexino-stm32:tiny):
text data bss dec hex filename
34884 328 1768 36980 9074 nuttx
after this change:
text data bss dec hex filename
35052 340 1768 37160 9128 nuttx
delta
text data bss dec hex filename
168 12 0 180 b4 nuttx
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
