spi: s3c64xx: describe driver in KConfig

Describe better which driver applies to which SoC, to make configuring
kernel for Samsung SoC easier.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210924133114.111777-1-krzysztof.kozlowski@canonical.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/Kconfig

@@ -747,10 +747,11 @@ config SPI_S3C24XX_FIQ
 	  TX and RX data paths.
 
 config SPI_S3C64XX
-	tristate "Samsung S3C64XX series type SPI"
+	tristate "Samsung S3C64XX/Exynos SoC series type SPI"
 	depends on (PLAT_SAMSUNG || ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST)
 	help
-	  SPI driver for Samsung S3C64XX and newer SoCs.
+	  SPI driver for Samsung S3C64XX, S5Pv210 and Exynos SoCs.
+	  Choose Y/M here only if you build for such Samsung SoC.
 
 config SPI_SC18IS602
 	tristate "NXP SC18IS602/602B/603 I2C to SPI bridge"