m68k: mvme147: Make mvme147_init_IRQ() static

When building with W=1:

    arch/m68k/mvme147/config.c:76:13: warning: no previous prototype for ‘mvme147_init_IRQ’ [-Wmissing-prototypes]
       76 | void __init mvme147_init_IRQ(void)
	  |             ^~~~~~~~~~~~~~~~

Fix this by making mvme147_init_IRQ() static.
The function body was moved to arch/m68k/mvme147/config.c in v2.6.18.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/853e29ca81761032c3af132fffbd583b667234a6.1694613528.git.geert@linux-m68k.org