mailbox: remove unneeded double quotation

It makes Kconfig strange. fix it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: morimoto

drivers/mailbox/Kconfig

@@ -279,7 +279,7 @@ config MTK_ADSP_MBOX
 	tristate "MediaTek ADSP Mailbox Controller"
 	depends on ARCH_MEDIATEK || COMPILE_TEST
 	help
-          Say yes here to add support for "MediaTek ADSP Mailbox Controller.
+          Say yes here to add support for MediaTek ADSP Mailbox Controller.
           This mailbox driver is used to send notification or short message
           between processors with ADSP. It will place the message to share
 	  buffer and will access the ipc control.