mb/google/skyrim: Expand cbmem console buffer

Expand the size of cbmem console buffer from default value 0x20000 to
0x80000. Verified by running "cbmem -l" in Chromium OS shell.

localhost ~ # cbmem -l
CBMEM table of contents:
    NAME          ID           START      LENGTH
 0. FSP MEMORY  46535052  b97fe000   01000000
 1. CONSOLE     434f4e53  b977e000   00080000
 2. RW MCACHE   574d5346  b977d000   00000360
 3. RO MCACHE   524d5346  b977c000   00000f20
 4. FMAP        464d4150  b977b000   0000047c
 5. TIME STAMP  54494d45  b977a000   00000910
 6. VBOOT WORK  78007343  b9766000   00014000
 7. RAMSTAGE    9a357a9e  b9700000   00066000
 8. ACPI BERT   42455254  b96fc000   00004000
 9. CHROMEOS NVS        434e5653  b96fb000   00000f00
10. REFCODE     04efc0de  b96ab000   00050000
11. MEM INFO    494d454d  b96aa000   00000768
12. RAMOOPS     05430095  b95aa000   00100000
13. COREBOOT    43425442  b95a2000   00008000
14. ACPI        41435049  b957e000   00024000
15. TPM2 TCGLOG 54504d32  b956e000   00010000
16. SMBIOS      534d4254  b9566000   00008000
17. FSP RUNTIME 52505346  ba7febe0   00000004
18. POWER STATE 50535454  ba7feb80   00000060
19. ROMSTAGE    47545352  ba7feb60   00000004
20. EARLY DRAM USAGE    4544524d  ba7feb40   00000008
21. ACPI GNVS   474e5653  ba7feb20   00000020

BUG=246268888
TEST=Skyrim

Change-Id: I79205f31b4cc3276c1c213a171a6bf7e18d73a1c
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68293
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>

src/mainboard/google/skyrim/Kconfig

@@ -139,4 +139,8 @@ config OVERRIDE_EFS_SPI_SPEED_MIN_BOARD
 	  Minimum board version starting which the Override EFS SPI Speed
 	  configuration has to be applied.
 
+config CONSOLE_CBMEM_BUFFER_SIZE
+	hex
+	default 0x80000
+
 endif # BOARD_GOOGLE_BASEBOARD_SKYRIM