serial: renesas: Fix R-Car spelling

The correct spelling is R-Car, including the dash, update the usage.
Kconfig strings and comment changes only, no functional change.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 8b27ad9..c4f4a8d 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -920,7 +920,7 @@
 	depends on SH || ARCH_RENESAS
 	help
 	  Select this to enable Renesas SCIF UART. To operate serial ports
-	  on systems with RCar or SH SoCs, say Y to this option. If unsure,
+	  on systems with R-Car or SH SoCs, say Y to this option. If unsure,
 	  say N.
 
 choice