Drop "Time" Workaround for Xilinx Vivado

[Paebbels]

PoC has two main branches: master and vivado. The latter was needed for a PoC wide workaround to implement the datatype TIME as REAL, because Vivado messed up that physical datatype. Nowadays, that datatype is fixed since Vivado 2019.2.

Moreover, Git started to rename the master branch to main.

To reduce PoC's complexity, unify the master and vivado branches into main.