sh: Fix fallout from ZERO_PAGE consolidation

Consolidation of empty_zero_page declarations broke boot on sh.

sh stores its initial boot parameters in a page reserved in
arch/sh/kernel/head_32.S. Before commit 6215d9f4 ("arch, mm:
consolidate empty_zero_page") this page was referenced in C code
as an array and after that commit it is referenced as a pointer.

This causes wrong code generation and boot hang.

Declare boot_params_page as an array to fix the issue.

Reported-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Tested-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Fixes: 6215d9f4 ("arch, mm: consolidate empty_zero_page")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>