This commit adds a system utily 'stty' to NuttX, providing a standard
Unix-like interface for configuring terminal (TTY) device settings.
The command allows runtime configuration of termios attributes for
serial ports and other character devices.
Usage examples:
# Set raw mode on ttyS0 (for binary communication)
nsh> stty -F /dev/ttyS0 raw -echo
# Set console mode for interactive terminal
nsh> stty -F /dev/ttyS0 cooked
# Display current settings
nsh> stty -F /dev/ttyS0
# Configure stdin (if it's a TTY)
nsh> stty echo icanon
# Set baudrate (if driver support)
nsh> stty -F /dev/ttyS1 speed 115200
Signed-off-by: fangpeina <fangpeina@xiaomi.com>
