intel_s1000: define memctl_default.S and memerror-vector.S files

Define memctl_default.S and memerror-vector.S files. A reference
could be found in the Xtensa toolchain directories. These are
required for using cavs21_LX6HiFi3_RF3_WB16 Xtensa CPU mainly in
simulator. On boards which have ROM, these would have been already
defined in the ROM. Hence, the contents of these files will be
developed at a later time if required.

Change-Id: Idf52397bb6880c136525e69f47e09defcba7f036
Signed-off-by: Rajavardhan Gundi <rajavardhan.gundi@intel.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>