hwrng: ba431 - HW_RANDOM_BA431 should not default to y

As HW_RANDOM_BA431 does not have any platform dependency, it should not
default to enabled.

Fixes: 0289e9be ("hwrng: ba431 - add support for BA431 hwrng")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/Kconfig

@@ -77,7 +77,6 @@ config HW_RANDOM_ATMEL
 config HW_RANDOM_BA431
 	tristate "Silex Insight BA431 Random Number Generator support"
 	depends on HAS_IOMEM
-	default HW_RANDOM
 	help
 	  This driver provides kernel-side support for the Random Number
 	  Generator hardware based on Silex Insight BA431 IP.
@@ -85,8 +84,6 @@ config HW_RANDOM_BA431
 	  To compile this driver as a module, choose M here: the
 	  module will be called ba431-rng.
 
-	  If unsure, say Y.
-
 config HW_RANDOM_BCM2835
 	tristate "Broadcom BCM2835/BCM63xx Random Number Generator support"
 	depends on ARCH_BCM2835 || ARCH_BCM_NSP || ARCH_BCM_5301X || \