configure: gcov should not exclude fortify-source

There is no reason other than history (dating back to commit 1d728c39, "tests: add gcov
support", 2013-01-06) for this, remove this unnecessary conditional.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -2625,9 +2625,7 @@ fi
 
 write_c_skeleton
 
-if test "$gcov" = "yes" ; then
-  :
-elif test "$fortify_source" = "yes" ; then
+if test "$fortify_source" = "yes" ; then
   QEMU_CFLAGS="-U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $QEMU_CFLAGS"
   debug=no
 fi