OvmfPkg: remove PcdMaxHardwareErrorVariableSize from the DSC files

OvmfPkg: remove PcdMaxHardwareErrorVariableSize from the DSC files

PcdMaxHardwareErrorVariableSize sets the size limit for individual
Hardware Error Record Variables (see "7.2.3 Hardware Error Record
Persistence" and "Appendix P, Hardware Error Record Persistence Usage" in
the UEFI-2.6 spec).

Since Hardware Error Record Persistence is an optional firmware feature,
according to the spec, and OVMF does not enable it -- it inherits
PcdHwErrStorageSize and PcdHardwareErrorRecordLevel with zero values --,
the PcdMaxHardwareErrorVariableSize setting in our DSC files has no
effect. Remove it in order to eliminate future confusion.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Suggested-by: Star Zeng <star.zeng@intel.com>
Ref: http://thread.gmane.org/gmane.comp.bios.edk2.devel/9743/focus=9780
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>