Remove Kconfig variable that has no effect

CPU_HAS_BOOTBLOCK_INIT is only declared once and selected elsewhere
(with no overlap), and never read. Remove it.

Change-Id: I3f294b0724a87876a7e2f274e6933fe10321a69d
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10253
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/arch/riscv/Kconfig

@@ -25,10 +25,6 @@ config RISCV_BOOTBLOCK_CUSTOM
 	bool
 	default n
 
-config CPU_HAS_BOOTBLOCK_INIT
-	bool
-	default n
-
 config MAINBOARD_HAS_BOOTBLOCK_INIT
 	bool
 	default n