FixesARMmbed/mbed-os#15498
Adds 2 boolean flags to the STM32 `i2c_s` object
to indicate whether a transfer is in progress,
separate from the existing "transfer pending" flags.
`i2c_slave_write`, `i2c_slave_read` and their associated callbacks
are modified to use these flags in addition to the pending flags.
The original behavior of the pending flags is preserved.
Use uint16_t variables for i2c slave_rx_buffer_size and slave_rx_count
variables. This allows to receive more than 255 bytes in slave mode. The
bytes are received one by one in slave mode so there are no hardware
limitations forcing a 1 byte rx count limit.
Adam Gausmann
Mathieu Othacehe
pennam
jeromecoutant