drm/i915/pps: rename intel_power_sequencer_reset to intel_pps_reset_all

Follow the usual naming pattern for functions. "reset all" because it
iterates over all DP encoders. No functional changes.

Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b10013e2c976ca140b1ad62669e18a2e9f1e8c35.1610127741.git.jani.nikula@intel.com