Change DW_LLE_baseaddr to DW_LLE_baseaddrx in .debug_loclist section

With https://reviews.llvm.org/D154638, the ability to emit a .debug_addr
section has been added to dsymutil. With this, instead of emitting a
DW_LLE_baseaddr in the .debug_loclist section, a DW_LLE_baseaddrx can be
emitted instead, which will allow for more indirection.

Differetial Revision: https://reviews.llvm.org/D155724