arch/x86: Remove most C_ENV_BOOTBLOCK_SIZE limits

With top-aligned bootblock this is no longer globally needed.
The default maximum is now a generous 256 KiB with couple
platforms having lower limits of 32 KiB and 64 KiB.

Change-Id: Ib1aee44908c0dcbc17978d3ee53bd05a6200410c
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47600
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

configs/config.facebook_fbg1701.mboot_vboot

@@ -1,5 +1,4 @@
 CONFIG_VENDOR_FACEBOOK=y
-CONFIG_C_ENV_BOOTBLOCK_SIZE=0x6000
 CONFIG_ONBOARD_SAMSUNG_MEM=y
 CONFIG_CPU_MICROCODE_CBFS_LOC=0xFFF8B000
 CONFIG_CPU_MICROCODE_CBFS_EXTERNAL_BINS=y