sml bus decoder syntax update

[gemu2015]

support for byte order

Description:

bus decoder syntax support for byte oder

upper case means high order byte

unsigned 16,32 bit
UUuu or uuUU
UUuuUUuu
signed 16,32 bit
SSss or ssSS
SSssSSss

Checklist:

• The pull request is done against the latest dev branch
• Only relevant files were touched
• Only one feature/fix was added per PR.
• The code change is tested and works on core 2.6.1
• The code change pass travis tests. Your PR cannot be merged unless tests pass
• I accept the CLA.