Update embedded-hal to 1.0.0-alpha.7.

[reitermarkus]

PWM traits have been removed for now, see rust-embedded/embedded-hal#358.

There is a new transaction function required for the I2c trait. I have not implemented this for now since I don't want to reinvent the wheel. The same functionality is already available via https://github.com/rust-embedded/linux-embedded-hal. Both are using the Linux device, so I don't think there is any difference except implementation details.

[golemparts]

Thanks for the continued updates! I briefly looked at the transaction function, which should be easy enough to implement with an I2C_RDWR ioctl() request. I think it makes sense for me to add that feature to rppal's own I2c first, after which support can be added for embedded-hal.