mfd: madera: Add missing of table registration

MODULE_DEVICE_TABLE(of, <of_match_table>) should be called to complete DT
OF mathing mechanism and register it.

Before this patch:
modinfo ./drivers/mfd/madera.ko | grep alias

After this patch:
modinfo ./drivers/mfd/madera.ko | grep alias
alias:          of:N*T*Ccirrus,wm1840C*
alias:          of:N*T*Ccirrus,wm1840
alias:          of:N*T*Ccirrus,cs47l91C*
alias:          of:N*T*Ccirrus,cs47l91
alias:          of:N*T*Ccirrus,cs47l90C*
alias:          of:N*T*Ccirrus,cs47l90
alias:          of:N*T*Ccirrus,cs47l85C*
alias:          of:N*T*Ccirrus,cs47l85
alias:          of:N*T*Ccirrus,cs47l35C*
alias:          of:N*T*Ccirrus,cs47l35
Reported-by: Javier Martinez Canillas <javier@dowhile0.org>
Signed-off-by: Daniel Gomez <dagmcr@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/madera-core.c

@@ -286,6 +286,7 @@ const struct of_device_id madera_of_match[] = {
 	{ .compatible = "cirrus,wm1840", .data = (void *)WM1840 },
 	{}
 };
+MODULE_DEVICE_TABLE(of, madera_of_match);
 EXPORT_SYMBOL_GPL(madera_of_match);
 
 static int madera_get_reset_gpio(struct madera *madera)