Move llvm_init_inner inside #ifdef ENABLE_LLVM

This should fix c30a3e4 failing to link properly with ld 2.22 and GCC 4.9.1, on Linux, with non-LLVM builds.

./.libs/libmini.a(libmini_la-mini.o): In function `llvm_init_inner':
mini.c:(.text+0x1182b): undefined reference to `mono_llvm_init'
/usr/bin/ld: .libs/libmonoboehm-2.0.so.1.0.0: hidden symbol `mono_llvm_init' isn't defined
/usr/bin/ld: final link failed: Bad value

mono/mini/mini.c

@@ -7274,6 +7274,7 @@ mini_free_jit_domain_info (MonoDomain *domain)
 	domain->runtime_info = NULL;
 }
 
+#ifdef ENABLE_LLVM
 static gboolean
 llvm_init_inner (void)
 {
@@ -7283,6 +7284,7 @@ llvm_init_inner (void)
 	mono_llvm_init ();
 	return TRUE;
 }
+#endif
 
 /*
  * mini_llvm_init: