Build: Remove linkage section "SFN" and its helpers

The linkage section "SFN' is not necessary, so remove it
and its helper "_tfm_nspm_secure_gateway_attributes_".

Signed-off-by: Chendi Sun <chendi.sun@arm.com>
Change-Id: Ic11bd6cf2200c539631ff6b990b0d4a6a8831d8a
diff --git a/secure_fw/include/security_defs.h b/secure_fw/include/security_defs.h
index a776d8d..a048356 100644
--- a/secure_fw/include/security_defs.h
+++ b/secure_fw/include/security_defs.h
@@ -25,16 +25,16 @@
  * being renamed and cloned
  */
 #define __tz_c_veneer \
-        __attribute__((cmse_nonsecure_entry, noclone, section("SFN")))
+        __attribute__((cmse_nonsecure_entry, noclone))
 #define __tz_naked_veneer \
-        __attribute__((cmse_nonsecure_entry, noclone, naked, section("SFN")))
+        __attribute__((cmse_nonsecure_entry, noclone, naked))
 
 #else /* __GNUC__ && !__ARMCC_VERSION */
 
 #define __tz_c_veneer \
-        __attribute__((cmse_nonsecure_entry, section("SFN")))
+        __attribute__((cmse_nonsecure_entry))
 #define __tz_naked_veneer \
-        __attribute__((cmse_nonsecure_entry, naked, section("SFN")))
+        __attribute__((cmse_nonsecure_entry, naked))
 
 #endif /* __GNUC__ && !__ARMCC_VERSION */