edac: cortex_arm64: Use device tree property for CTI PMU Workaround

The CTI PMU workaround is enabled by default. Use a device tree property
to decide if the workaround needs to be applied or not.

Change-Id: Iaa847b7309d204d41c0ca53984964f3b238e0427
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>