sh: sh7757lcr: Make init_sh7757lcr_IRQ() static

arch/sh/boards/board-sh7757lcr.c:572:13: warning: no previous prototype for 'init_sh7757lcr_IRQ' [-Wmissing-prototypes]

There are no users outside this file, so make it static.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/fba00424b5b0bee0f9b9cbc63d649a86854d202f.1709579038.git.geert+renesas@glider.be


Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>