serial: sh: Rename CONFIG_SCI and CONFIG_SCIF_USE_EXT_CLK to CFG_ variants

Both CONFIG_SCI and CONFIG_SCIF_USE_EXT_CLK options do not have a
matching Kconfig entry because they are internal to the SCIF driver.
Change their prefix to CFG_, i.e. CFG_SCIF_USE_EXT_CLK and CFG_SCI,
to reflect that and avoid interferring with Kconfig symbols. Since
neither of those options are defined elsewhere, no functional change.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
diff --git a/drivers/serial/serial_sh.c b/drivers/serial/serial_sh.c
index 4671217..c3e3f25 100644
--- a/drivers/serial/serial_sh.c
+++ b/drivers/serial/serial_sh.c
@@ -276,7 +276,7 @@
 
 #if defined(CFG_SCIF_A)
 	#define SCIF_BASE_PORT	PORT_SCIFA
-#elif defined(CONFIG_SCI)
+#elif defined(CFG_SCI)
 	#define SCIF_BASE_PORT  PORT_SCI
 #else
 	#define SCIF_BASE_PORT	PORT_SCIF
@@ -286,7 +286,7 @@
 	.membase	= (unsigned char *)SCIF_BASE,
 	.mapbase	= SCIF_BASE,
 	.type		= SCIF_BASE_PORT,
-#ifdef CONFIG_SCIF_USE_EXT_CLK
+#ifdef CFG_SCIF_USE_EXT_CLK
 	.clk_mode =	EXT_CLK,
 #endif
 };