[ARM] support tracing when using newer compilers

Since gcc 4.4 the name and calling convention for function profiling
on ARM changed.  With this patch both types are supported.

See http://sourceware.org/ml/libc-ports/2008-04/msg00009.html for some
details.

Lightly-Tested-by: Anand Gadiyar <gadiyar@ti.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

arch/arm/include/asm/ftrace.h

@@ -7,6 +7,7 @@
 
 #ifndef __ASSEMBLY__
 extern void mcount(void);
+extern void __gnu_mcount_nc(void);
 #endif
 
 #endif