machine/i2c already uses mp_hal_get_pin_obj which
points to pin_find function in order to locate correct
pin object to use.
The pin_find function was recently updated to also
being able to locate pins based on an integer value,
such that pin number can be used as argument to object
constructors.
This patch modfies and uniforms pin object lookup for
SPI, music and pwm.
3209a13bf5