Modify SDK to fit Arduino core

These are the changes that were required to get compiling with the new 2.2.0 source code

1. Remove 'am_util_regdump.c' -- contained references to instance finder names like 'AM_REG_ITM_NUM_MODULES' that were not declared in any included headers. Could not track down include path to the appropriate header ('am_regs.h'?) so decided to simply remove this compilation unit. Register dump utilities will be unavailable, but they are an obscure feature.
1. Made internal stdio buffer available for use by 'uart' code (avoids doubling up resources required for printf)

Author: oclyke