drivers/smmstore: Implement SMMSTORE version 2

SMMSTORE version 2 is a complete redesign of the current driver. It is
not backwards-compatible with version 1, and only one version can be
used at a time.

Key features:
* Uses a fixed communication buffer instead of writing to arbitrary
  memory addresses provided by untrusted ring0 code.
* Gives the caller full control over the used data format.
* Splits the store into smaller chunks to allow fault tolerant updates.
* Doesn't provide feedback about the actual read/written bytes, just
  returns error or success in registers.
* Returns an error if the requested operation would overflow the
  communication buffer.

Separate the SMMSTORE into 64 KiB blocks that can individually be
read/written/erased. To be used by payloads that implement a
FaultTolerant Variable store like TianoCore.

The implementation has been tested against EDK2 master.

An example EDK2 implementation can be found here:
eb1127744a

Change-Id: I25e49d184135710f3e6dd1ad3bed95de950fe057
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Christian Walter <christian.walter@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40520
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>

src/lib/coreboot_table.c

@@ -20,6 +20,8 @@
 #include <spi_flash.h>
 #include <security/vboot/misc.h>
 #include <security/vboot/vbnv_layout.h>
+#include <smmstore.h>
+
 #if CONFIG(USE_OPTION_TABLE)
 #include <option_table.h>
 #endif
@@ -548,6 +550,10 @@ static uintptr_t write_coreboot_table(uintptr_t rom_table_end)
 
 	add_cbmem_pointers(head);
 
+	/* SMMSTORE v2 */
+	if (CONFIG(SMMSTORE_V2))
+		lb_smmstorev2(head);
+
 	/* Add board-specific table entries, if any. */
 	lb_board(head);