[U-Boot] serial: CONFIG_ARM_DCC_MULTI failures

[Michal Simek]

Hi Marek and others,

I have found that in uboot is arm-dcc driver (drivers/serial/arm_dcc.c)
which is
1. not compiled by any configuration
2. when it is enabled is causing compilation failures because of SERIAL_MULTI removal

The problem is with this code.

#ifndef CONFIG_ARM_DCC_MULTI
#define arm_dcc_init serial_init
void serial_setbrg(void) {}
#define arm_dcc_getc serial_getc
#define arm_dcc_putc serial_putc
#define arm_dcc_puts serial_puts
#define arm_dcc_tstc serial_tstc
#endif

It means that CONFIG_ARM_DCC_MULTI should be always enabled and we
can remove this option entirely. 

Then there is missing default_serial_console() if there is no
another serial driver.

Also I am sending the second patch which fix compilation warning.

Thanks,
Michal