The underlying peripheral can only read from RAM. This uses the
existing infrastructure (already needed to work around the lack of a
hardware support for I2C_NOSTART) to unconditionally copy any to-be-sent
data into RAM.
The I2C peripheral's shortcuts are used with the read and write register
to automatically stop the I2C transaction or to continue with the next
stage.
With simple I2C read and write bytes these shorts are not used, but are
also not cleared by the function in all cases, causing it to use the
shortcut configuration set by a previous function call. This patch
ensures that the shorts are always set by the read and write functions
