Now that the PUSHFRAME and PULLFRAME macros are used only in the swi
entry/exit code, they don't need to be macros.  Now they're just inline
code, and rewritten to use shorter instruction sequences.
Pass the actual baudrate to tty_init_console(). This defines the initial
baudrate of the device special file, and makes sure that on open(2) the
UART is programmed with the correct baudrate. This then eliminates the
need in uart_tty_param() to override the speed setting.