Cleanup ledc driver

Removes an include for a file that does not exist. It was dropped during the PR introducing the ledc
driver, but the include line was left, as well as several uses of macros defined in the file.

Removes undefined macros, replacing them with their values, and documents the meaning of the values.

Signed-off-by: Winford <winford@object.stream>

Author: UncleGrumpy

libs/eavmlib/src/ledc.erl

@@ -45,13 +45,13 @@
     stop/3
 ]).
 
--include("ledc.hrl").
-
 -type duty_resolution() :: non_neg_integer().
 -type duty_resolution_cfg() :: {duty_resolution, duty_resolution()}.
 -type freq_hz() :: non_neg_integer().
 -type freq_hz_cfg() :: {freq_hz, freq_hz()}.
--type speed_mode() :: ?LEDC_LOW_SPEED_MODE | ?LEDC_HIGH_SPEED_MODE.
+-type speed_mode() :: 0 | 1.
+%% Speed modes: use `0' for high speed, `1' for low speed.
+
 -type speed_mode_cfg() :: {speed_mode, speed_mode()}.
 -type timer_num() :: 0..3.
 -type timer_num_cfg() :: {timer_num, timer_num()}.