block/partitions/ldm: Remove redundant assignments

block/partitions/ldm: Remove redundant assignments

Get rid of the following redundant assignments:
- to a variable r_cols from function ldm_parse_cmp3
- to variables r_id1 and r_id2 from functions ldm_parse_dgr3 and ldm_parse_dgr4
- to a variable r_index from function ldm_parse_prt3
that end up in values not being read until the end of function.

Reported by clang-tidy [deadcode.DeadStores]

Signed-off-by: Michal Orzel <michalorzel.eng@gmail.com>
Link: https://lore.kernel.org/r/20220423113811.13335-5-michalorzel.eng@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>