soc/intel/alderlake: Change VBOOT_HASH_BLOCK_SIZE to 4 KiB

Default VBOOT_HASH_BLOCK_SIZE is 1 KiB and increasing it to 4 KiB
helps in improving overall boot time since it reduces hashing and
body loading time.

Increasing it over 4 KiB doesn't result in significant improvement,
thus keeping the value at 4 KiB as of now.

Timing data:
Note that before Data is with 1 KiB block size.
|------------------------------------------------------|
|        Stage        | Block Size | Before  |  After  |
|finished loading body|     4 KiB  | 205,187 | 189,947 |
|finished loading body|     8 KiB  | 205,187 | 188,708 |
|finished loading body|    16 KiB  | 205,187 | 188,085 |
|finished loading body|    32 KiB  | 205,187 | 187,793 |
|------------------------------------------------------|

BUG=b:188577893
BRANCH=None
TEST=Boot time for Brya improves by 20 - 25 msec

Change-Id: I9222761c7d58e4a370d3a41c651b6c169599d792
Signed-off-by: MAULIK V VAGHELA <maulik.v.vaghela@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57141
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/soc/intel/alderlake/Kconfig

@@ -260,6 +260,13 @@ config VBOOT
 	select VBOOT_VBNV_CMOS_BACKUP_TO_FLASH
 	select VBOOT_X86_SHA256_ACCELERATION
 
+# Default hash block size is 1KiB. Increasing it to 4KiB to improve
+# hashing time as well as read time. This helps in improving
+# boot time for Alder Lake.
+config VBOOT_HASH_BLOCK_SIZE
+	hex
+	default 0x1000
+
 config CBFS_SIZE
 	default 0x200000