arm64: dts: qcom: sc7280: Add 3ms ramp to herobrine's pp3300_left_in_mlb

arm64: dts: qcom: sc7280: Add 3ms ramp to herobrine's pp3300_left_in_mlb

The "pp3300_left_in_mlb" rail on herobrine eventually connects up to
"vreg_edp_3p3" on the qcard. On several herobrine designs this rail
has been measured to need more than 1ms to turn on.

While technically a herobrine derivative (defined as anyone including
the "herobrine.dtsi") could change the board to make the rail rise
faster or slower, the fact that two boards (evoker and villager) both
measured it as taking more than 1ms implies that it's probably going
to be the norm. Thus, let's add a "regulator-enable-ramp-delay"
straight into the herobrine.dtsi to handle this. If a particular
derivative board needs a faster or slower one then they can override
it, though that feels unlikely.

While we measured something a bit over 1ms, we'll choose 3ms to give
us a tiny bit of margin. This isn't a rail that turns off and on all
the time anyway and 3ms is nothing compared to the total amount of
time to power on a panel.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230206184744.2.I13814cefc5ab3e0a39ebd09f052e3fd25d4e8f1d@changeid