[PATCH] kbuild: modpost needs to cope with new glibc elf header on sparc

Recently a change in the glibc elf.h header has been introduced causing
modpost to spawn tons of warnings (like the one below) building the kernel
on sparc:

[SNIP]
*** Warning: "current_thread_info_reg" [net/sunrpc/auth_gss/auth_rpcgss.ko] undefined!
*** Warning: "" [net/sunrpc/auth_gss/auth_rpcgss.ko] undefined!
*** Warning: "" [net/sunrpc/auth_gss/auth_rpcgss.ko] undefined!
[SNIP]

Ben Collins discovered that the STT_REGISTERED definition in glibc did change
and that this change needs to be propagated to modpost.

glibc change:
-#define STT_REGISTER   13              /* Global register reserved to app. */
+#define STT_SPARC_REGISTER     13      /* Global register reserved to app. */

I did and tested this simple patch to maintain compatibility with newer (>= 2.3.4)
and older (<= 2.3.2) glibc.

Signed-off-by: Fabio M. Di Nitto <fabbione@fabbione.net>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>