cpu: split LTAGE implementation into a base TAGE and a derived LTAGE

cpu: split LTAGE implementation into a base TAGE and a derived LTAGE

The new derived LTAGE is equivalent to the original LTAGE implementation
The default values of the TAGE branch predictor match the settings of the
8C-TAGE configuration described in https://www.jilp.org/vol8/v8paper1.pdf

Change-Id: I8323adbfd5c9a45db23cfff234218280e639f9ed
Signed-off-by: Pau Cabre <pau.cabre@metempsy.com>
Reviewed-on: https://gem5-review.googlesource.com/c/14435
Reviewed-by: Sudhanshu Jha <sudhanshu.jha@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>