[LLDB] [PECOFF] Make sure to set the address byte size in m_data after parsing headers

If not set, the address byte size was implied to be the one of the
host process.

This allows reverting the functional change from 31087b2ae9154, since
now PECOFF does the same as ELF and MachO wrt setting both byte order
and address size on m_data within ParseHeader.

Differential Revision: https://reviews.llvm.org/D71108