Updates have been made to the baremetal examples.

CMake Updates

• The CMake file can now find riscv-none-elf-gcc as the xpack GCC executable has been renamed to riscv-none-elf-*.
• Recent GCCs/binutils require the zicsr extension to be specified in -march to use CSR instructions.

Code Updates

• Updated CSR access templates to test for zicsr extension.
• Updated the CSR access header for the Baremetal C examples.
• Fixed the CMakeLists.txt files to include -march=rv32imac_zicsr.
• Updated the timer.h to allow USEC/MSEC intervals and different timer frequencies.
• Added the baremetal-vcd-trace example.