ASLTS: Fixes for SMBUS/GSBUS region access tests

This patch makes corrections to serveral region tests that check operations on
GenericSerialBus and SMBus fields. These changes are required after commit
36a1179 corrected the size of the buffer that was calculated for each of the
different bus protocols.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Acpiexec: Set correct access length for SMBUS/GSBUS region test handler

Fixes a bug in the test handler for the SMBUS/GSBUS regions where the access
length for certain protocols was being incorrectly decremented by 2 to account
for the Status and Length bytes. This value already excludes the 2 bytes.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>