[AMDGPU] Revert wide LDS DMA support.

This reverts ffbee7ac, see also bug 37653 which it was fixing.
The bug claims this is an undocumented feature which actually works.
In the reality it is documented as not working for a good reason.
It likely does something, but it is useless anyway. These instructions
write into the LDS. The LDS address is:

M0 + inst_offset + (TIDinWave * 4).

For a store wider than a DWORD neighboring lanes will overwrite each
other.

Differential Revision: https://reviews.llvm.org/D125409