tools/testing/selftests/ptrace/peeksiginfo.c: add PAGE_SIZE definition

On IBM powerpc where multiple page size value are supported, current
ppc64 and ppc64el distro don't define the PAGE_SIZE variable in
/usr/include as this is a dynamic value retrieved by the getpagesize()
or sysconf() defined in unistd.h. The PAGE_SIZE variable sounds defined
when only one value is supported by the kernel.

As such, when the PAGE_SIZE definition doesn't exist system should
retrieve the dynamic value.

Signed-off-by: Thierry Fauck <[e-mail]>
Cc: Andrey Vagin <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

tools/testing/selftests/ptrace/peeksiginfo.c

···
 #define TEST_SICODE_PRIV	-1
 #define TEST_SICODE_SHARE	-2
 
+#ifndef PAGE_SIZE
+#define PAGE_SIZE sysconf(_SC_PAGESIZE)
+#endif
+
 #define err(fmt, ...)						\
 		fprintf(stderr,					\
 			"Error (%s:%d): " fmt,			\