altera_uart: Fix missing prototype for registering an early console

Simply add an early_altera_uart_setup() prototype declaration, otherwise
platform code have to do it in .c files, which is ugly.

Signed-off-by: Anton Vorontsov <[e-mail]>
Acked-by: Tobias Klauser <[e-mail]>
Cc: Alan Cox <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

include/linux/altera_uart.h

···
 #ifndef	__ALTUART_H
 #define	__ALTUART_H
 
+#include <linux/init.h>
+
 struct altera_uart_platform_uart {
 	unsigned long mapbase;	/* Physical address base */
 	unsigned int irq;	/* Interrupt vector */
 	unsigned int uartclk;	/* UART clock rate */
 	unsigned int bus_shift;	/* Bus shift (address stride) */
 };
+
+int __init early_altera_uart_setup(struct altera_uart_platform_uart *platp);
 
 #endif /* __ALTUART_H */