fix(errata): workaround for Cortex-A78C 2132064

fix(errata): workaround for Cortex-A78C 2132064

Cortex-A78C erratum 2132064 is a cat B erratum that applies to revisions
r0p1 and r0p2 and is still open.

This patch implements workaround option 2 that places the data
prefetcher in the most conservative mode to greatly reduce prefetches
by writing the following bits to the value indicated:
ecltr[7:6], PF_MODE = 2'b11

SDEN can be found here:
https://developer.arm.com/documentation/SDEN2004089/latest

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: Ica2561c1e257643c2482085447ef852fa62a1eb2