CDC-ACM - Fix slow write() performance and availableForWrite() logic
CDC-ACM - Fix slow write() performance and availableForWrite() logic

- Removed delay in write() function which caused slow TX performance
- Removed timeout logic in write() function; moved to LMT side
- Fixed logic in availableForWrite() - ring-buffer capacity is at most
  1 less than actual size to avoid head index passing tail index

Signed-off-by: Dan O'Donovan <2591e5f46f28d303f9dc027d475a5c60d8dea17a@emutex.com>

SidLeung/corelibs-arduino101,sandeepmistry/corelibs-arduino101,01org/corelibs-arduino101,linrjing/corelibs-arduino101,bigdinotech/corelibs-arduino101,sgbihu/corelibs-arduino101,01org/corelibs-arduino101,eriknyquist/corelibs-arduino101,sandeepmistry/corelibs-arduino101,bigdinotech/corelibs-arduino101,yashaswini-hanji/corelibs-arduino101,01org/corelibs-arduino101,sgbihu/corelibs-arduino101,yashaswini-hanji/corelibs-arduino101,linrjing/corelibs-arduino101,eriknyquist/corelibs-arduino101,SidLeung/corelibs-arduino101,sgbihu/corelibs-arduino101,bigdinotech/corelibs-arduino101,yashaswini-hanji/corelibs-arduino101,sandeepmistry/corelibs-arduino101,facchinm/corelibs-arduino101,facchinm/corelibs-arduino101