xtensa: fix declaration of _SecondaryResetVector_text_*

Secondary reset vector is defined, compiled and used when
CONFIG_SECONDARY_RESET_VECTOR is enabled, not only on SMP.
Make declarations of _SecondaryResetVector_text_* symbols available
accordingly.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/include/asm/sections.h

@@ -29,7 +29,7 @@ extern char _Level5InterruptVector_text_end[];
 extern char _Level6InterruptVector_text_start[];
 extern char _Level6InterruptVector_text_end[];
 #endif
-#ifdef CONFIG_SMP
+#ifdef CONFIG_SECONDARY_RESET_VECTOR
 extern char _SecondaryResetVector_text_start[];
 extern char _SecondaryResetVector_text_end[];
 #endif