Revert "Revert "Add prebuilt bootloader var and add bootloader t..."

Revert submission 1411608-revert-1402265-cf-x86-bootloader-XGKLNEQAPF

Reason for revert: Breakage originally caused by change was fixed. Refer to tracking bug for details.
Reverted Changes:
I89e95d4a6:Revert "Add prebuilt bootloader var and add bootlo...
I8fe199351:Revert "Added bootloader binary to cf x86 based ta...

Bug: 166380489
Bug: 164917252
Test: local build and Treehugger build
Change-Id: Ia895aedd77f2ec825aefecaf74c6dfc1ce631c93