arm/arm64: Generalize bootblock C entry point

When we first added ARM support to coreboot, it was clear that the
bootblock would need to do vastly different tasks than on x86, so we
moved its main logic under arch/. Now that we have several more
architectures, it turns out (as with so many things lately) that x86 is
really the odd one out, and all the others are trying to do pretty much
the same thing. This has already caused maintenance issues as the ARM32
bootblock developed and less-mature architectures were left behind with
old cruft.

This patch tries to address that problem by centralizing that logic
under lib/ for use by all architectures/SoCs that don't explicitly
opt-out (with the slightly adapted existing BOOTBLOCK_CUSTOM option).
This works great out of the box for ARM32 and ARM64. It could probably
be easily applied to MIPS and RISCV as well, but I don't have any of
those boards to test so I'll mark them as BOOTBLOCK_CUSTOM for now and
leave that for later cleanup.

BRANCH=None
BUG=None
TEST=Built Jerry and Falco, booted Oak.

Change-Id: Ibbf727ad93651e388aef20e76f03f5567f9860cb
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/12076
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/arch/riscv/Kconfig

@@ -6,6 +6,7 @@ config ARCH_BOOTBLOCK_RISCV
 	bool
 	default n
 	select ARCH_RISCV
+	select BOOTBLOCK_CUSTOM
 
 config ARCH_VERSTAGE_RISCV
 	bool
@@ -18,9 +19,3 @@ config ARCH_ROMSTAGE_RISCV
 config ARCH_RAMSTAGE_RISCV
 	bool
 	default n
-
-# If a custom bootblock is necessary, this option should be "select"-ed by
-# the thing that needs it, probably the CPU.
-config RISCV_BOOTBLOCK_CUSTOM
-	bool
-	default n

src/arch/riscv/bootblock_simple.c

@@ -14,7 +14,6 @@
  * GNU General Public License for more details.
  */
 
-#include <bootblock_common.h>
 #include <arch/cache.h>
 #include <arch/hlt.h>
 #include <arch/stages.h>

src/arch/riscv/include/bootblock_common.h

@@ -1,16 +0,0 @@
-#ifdef CONFIG_BOOTBLOCK_CPU_INIT
-#include CONFIG_BOOTBLOCK_CPU_INIT
-#endif
-
-// I'm disappointed that we let this kind of thing creep in.
-// we null out functions with this kind of stuff, AND weak symbols,
-// AND empty cpp function defines. What's next? Ouija boards?
-#if 0
-#ifdef CONFIG_BOOTBLOCK_MAINBOARD_INIT
-#include CONFIG_BOOTBLOCK_MAINBOARD_INIT
-#else
-static void bootblock_mainboard_init(void)
-{
-}
-#endif
-#endif