m68k/nommu: add missing definition of ARCH_PFN_OFFSET

Patch series "fixups for generic implementation of pfn_valid()".

Guenter reported boot failures on m68k-nommu and sh caused by the switch to
the generic implementation of pfn_valid():

https://lore.kernel.org/all/20230212173513.GA4052259@roeck-us.net
https://lore.kernel.org/all/20230212161320.GA3784076@roeck-us.net

These are small fixups that address the issues.


This patch (of 2):

On m68k/nommu RAM does not necessarily start at 0x0 and when it does not
pfn_valid() uses a wrong offset into the memory map which causes silent
boot failures.

Define ARCH_PFN_OFFSET to make pfn_valid() use the correct offset.

Link: https://lkml.kernel.org/r/20230214140729.1649961-1-rppt@kernel.org
Link: https://lkml.kernel.org/r/20230214140729.1649961-2-rppt@kernel.org
Fixes: d82f07f0 ("m68k: use asm-generic/memory_model.h for both MMU and !MMU")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Acked-by: Greg Ungerer <gerg@linux-m68k.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/m68k/include/asm/page_no.h

@@ -28,6 +28,8 @@ extern unsigned long memory_end;
 #define	virt_addr_valid(kaddr)	(((unsigned long)(kaddr) >= PAGE_OFFSET) && \
 				((unsigned long)(kaddr) < memory_end))
 
+#define ARCH_PFN_OFFSET PHYS_PFN(PAGE_OFFSET_RAW)
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _M68K_PAGE_NO_H */