Workaround for Neoverse N1 erratum 1800710

Workaround for Neoverse N1 erratum 1800710

Neoverse N1 erratum 1800710 is a Cat B erratum, present in older
revisions of the Neoverse N1 processor core.  The workaround is to
set a bit in the ECTLR_EL1 system register, which disables allocation
of splintered pages in the L2 TLB.

This errata is explained in this SDEN:
https://static.docs.arm.com/sden885747/f/Arm_Neoverse_N1_MP050_Software_Developer_Errata_Notice_v21.pdf

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Ie5b15c8bc3235e474a06a57c3ec70684361857a6