m68k: pull mach_beep in setup.c

It is possible to select INPUT_M68K_BEEP in a nommu configuration. This
results in the following link error:

drivers/input/misc/m68kspkr.o: In function `m68kspkr_event':
m68kspkr.c:(.text+0x3a): undefined reference to `mach_beep'
m68kspkr.c:(.text+0x5e): undefined reference to `mach_beep'
m68kspkr.c:(.text+0x78): undefined reference to `mach_beep'
drivers/input/misc/m68kspkr.o: In function `m68kspkr_init':
m68kspkr.c:(.init.text+0x4): undefined reference to `mach_beep'

Pull the mach_beep definition in setup.c to avoid it.

Signed-off-by: Alexandre Belloni <[e-mail]>
Acked-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Greg Ungerer <[e-mail]>

arch/m68k/kernel/setup.c

···
 #else
 #include "setup_no.c"
 #endif
+
+#if IS_ENABLED(CONFIG_INPUT_M68K_BEEP)
+void (*mach_beep)(unsigned int, unsigned int);
+EXPORT_SYMBOL(mach_beep);
+#endif

arch/m68k/kernel/setup_mm.c

···
 #ifdef CONFIG_M68K_L2_CACHE
 void (*mach_l2_flush) (int);
 #endif
-#if IS_ENABLED(CONFIG_INPUT_M68K_BEEP)
-void (*mach_beep)(unsigned int, unsigned int);
-EXPORT_SYMBOL(mach_beep);
-#endif
 #if defined(CONFIG_ISA) && defined(MULTI_ISA)
 int isa_type;
 int isa_sex;