serial: SH_SCI: improve "DMA support" prompt

Having a prompt of "DMA support" suddenly appear during a
"make oldconfig" can be confusing. Add a little helpful text to
the prompt message.

Fixes: 73a19e4 ("serial: sh-sci: Add DMA support.")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260110232643.3533351-5-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: rddunlap

drivers/tty/serial/Kconfig

@@ -671,7 +671,7 @@ config SERIAL_SH_SCI_EARLYCON
 	default ARCH_RENESAS
 
 config SERIAL_SH_SCI_DMA
-	bool "DMA support" if EXPERT
+	bool "Support for DMA on SuperH SCI(F)" if EXPERT
 	depends on SERIAL_SH_SCI && DMA_ENGINE
 	default ARCH_RENESAS