coreboot/skyrim: Enable signed PSP verstage

Enable signed PSP verstage for all skyrim variants along with increased
CBFS Mcache size.
* FW: 15261.0.0
* PSP: 00.3C.02.16
* Coreboot SHA: 7e25915cff1a3f37481e489c0bd37d9e89389db1

BUG=b:260603821
TEST=Build BIOS image for all Skyrim variants. Boot to OS in Skyrim and
confirm that PSP is in production mode. Perform suspend/resume cycles
for 100 iterations.

Change-Id: I82ea24e87553cb1a2e89c0cfc51687b3ca508d45
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/blobs/+/4065034
Reviewed-by: Chao Gui <chaogui@google.com>
Commit-Queue: Karthikeyan Ramasubramanian <kramasub@google.com>
Tested-by: Karthikeyan Ramasubramanian <kramasub@google.com>
3 files changed