tile: Define AT_VECTOR_SIZE_ARCH for ARCH_DLINFO

AT_VECTOR_SIZE_ARCH should be defined with the maximum number of
NEW_AUX_ENT entries that ARCH_DLINFO can contain, but it wasn't defined
for tile at all even though ARCH_DLINFO will contain one NEW_AUX_ENT for
the VDSO address.

This shouldn't be a problem as AT_VECTOR_SIZE_BASE includes space for
AT_BASE_PLATFORM which tile doesn't use, but lets define it now and add
the comment above ARCH_DLINFO as found in several other architectures to
remind future modifiers of ARCH_DLINFO to keep AT_VECTOR_SIZE_ARCH up to
date.

Fixes: 4a556f4f ("tile: implement gettimeofday() via vDSO")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>

arch/tile/include/asm/elf.h

@@ -129,6 +129,7 @@ extern int dump_task_regs(struct task_struct *, elf_gregset_t *);
 struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int executable_stack);
+/* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */
 #define ARCH_DLINFO \
 do { \
 	NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_BASE); \

arch/tile/include/uapi/asm/auxvec.h

@@ -18,4 +18,6 @@
 /* The vDSO location. */
 #define AT_SYSINFO_EHDR         33
 
+#define AT_VECTOR_SIZE_ARCH 1 /* entries in ARCH_DLINFO */
+
 #endif /* _ASM_TILE_AUXVEC_H */