wcaxx: Add extra dummy read when checking for single fxs modules.

This extra read eliminates some problems with detecting certain S100M modules.
It is unclear at this time why it is necessary.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>

drivers/dahdi/wcaxx-base.c

@@ -3610,6 +3610,10 @@ static bool check_for_single_fxs(struct wcaxx *wc, unsigned int port)
 	result = wcaxx_init_fxs_port(wc, mod);
 	if (!result)
 		mod->type = NONE;
+
+	/* It is currently unclear why this read is necessary for some of the
+	 * S100M modules to properly function. */
+	wcaxx_getreg(wc, mod, 0x00);
 	return result;
 }