mips: unify prom_putchar() declarations

prom_putchar() is used centrally in early printk infrastructure therefore
at least MIPS should agree on the function return type.

[paul.burton@mips.com:
  - Include linux/types.h in asm/setup.h to gain the bool typedef before
    we start include asm/setup.h elsewhere.
  - Include asm/setup.h in all files that use or define prom_putchar().
  - Also standardise on signed rather than unsigned char argument.]

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/19842/
Cc: linux-mips@linux-mips.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Jonas Gorski <jonas.gorski@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>

arch/mips/include/asm/setup.h

@@ -2,8 +2,10 @@
 #ifndef _MIPS_SETUP_H
 #define _MIPS_SETUP_H
 
+#include <linux/types.h>
 #include <uapi/asm/setup.h>
 
+extern void prom_putchar(char);
 extern void setup_early_printk(void);
 
 #ifdef CONFIG_EARLY_PRINTK_8250

arch/mips/include/asm/sgialib.h

@@ -31,7 +31,6 @@ extern int prom_flags;
 #define PROM_FLAG_DONT_FREE_TEMP	4
 
 /* Simple char-by-char console I/O. */
-extern void prom_putchar(char c);
 extern char prom_getchar(void);
 
 /* Get next memory descriptor after CURR, returns first descriptor

arch/mips/include/asm/txx9/generic.h

@@ -49,7 +49,6 @@ void txx9_spi_init(int busid, unsigned long base, int irq);
 void txx9_ethaddr_init(unsigned int id, unsigned char *ethaddr);
 void txx9_sio_init(unsigned long baseaddr, int irq,
 		   unsigned int line, unsigned int sclk, int nocts);
-void prom_putchar(char c);
 #ifdef CONFIG_EARLY_PRINTK
 extern void (*txx9_prom_putchar)(char c);
 void txx9_sio_putchar_init(unsigned long baseaddr);