0.4.2

The 0.4.2 imxrt-hal release contains three new peripherals, and a fix for existing peripheral errors.

Added

• Basic support for the secure real time clock (SRTC) peripheral, which
  continues to track time while the SNVS low-power domain remains powered.
• Add ADC channels. The channels implement the embedded-hal::adc::Oneshot
  trait.
• Preliminary support for the TRNG, with an implementation of embedded_hal's
  rng::Read trait. Includes support for rand_core::RngCore behind the
  optional "rand_core" feature.

Fixed

• Ensure that I2C and SPI errors can only be created by the HAL crate, and not by end users.