soc/amd/stoneyridge/smi.c: Prefer using '"%s...", __func__'

In function smm_setup_structures(), the function name is used in a print
string. Use __func__ instead.

BUG=b:117642170
TEST=Build grunt.

Change-Id: Icac5ea997289ef75fb246a09715cbca4442a57f4
Signed-off-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Reviewed-on: https://review.coreboot.org/29154
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/stoneyridge/smi.c

@@ -25,7 +25,7 @@
 
 void smm_setup_structures(void *gnvs, void *tcg, void *smi1)
 {
-	printk(BIOS_DEBUG, "smm_setup_structures STUB!!!\n");
+	printk(BIOS_DEBUG, "%s STUB!!!\n", __func__);
 }
 
 /** Set the EOS bit and enable SMI generation from southbridge */