realtek: pcs: rtl93xx: rename rxcal_ accessors to rxeq_

realtek: pcs: rtl93xx: rename rxcal_ accessors to rxeq_

Split naming convention: rxeq_* accessors control equalizer state
(get/set a coefficient, toggle adapt); rxcal_* functions run an actual
calibration procedure (measure, decide, retry). 930x's accessor layer
predates this split and still used rxcal_ throughout; rename it to
match the convention already applied consistently on 931x.

dfe_taps_adapt/dfe_disable move too - despite looping over TAP1-4,
they just apply a fixed control action with no measurement or
decision-making, same as the single-coefficient accessors. init,
fgcal, leq_adapt_lock and vth_tap0_adapt_lock stay rxcal_ - they're
the calibration-flow entry points that call these accessors as
building blocks, and the *_adapt_lock ones specifically read back a
result to decide what to lock in.

Also rename 931x's dfe_disable_5g to rxeq_dfe_disable_5g for the same
reason - it's a fixed control action, not a calibration procedure.

Link: https://github.com/openwrt/openwrt/pull/24542
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>