rtw88: use txpwr_lmt_cfg_pair struct, not arrays

We're just trusting that these tables are of the right dimensions, when
we could do better by just using the struct directly. Let's expose the
struct txpwr_lmt_cfg_pair instead.

The table changes were made by using some Vim macros, so that should
help prevent any translation mistakes along the way.

Remaining work: get the 'void *data' out of the generic struct
rtw_table; all of these tables really deserve to be their own data
structure, with proper type fields.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>