Instead of hard-coding var mtrr numbers in code, use this function to
identify the first available variable mtrr. If no such mtrr is
available, the function will return -1.
Change-Id: I2a1e02cdb45c0ab7e30609641977471eaa2431fd
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/14115
Tested-by: build bot (Jenkins)
Reviewed-by: Andrey Petrov <andrey.petrov@intel.com>