Write access using xChannelControlBlock may result in unexpected values in DPM when used on Big Endian targets

While it is possible to read/write to Channel Control Block via xChannelControlBlock(), endianess conversion is always performed after DPM access. Data shall be converted according to the desired access type.

Similarly, xChannelCommonStatusBlock() may return without DPM access due to errors and perform endianess conversion on the user buffer anyway (write access is prohibited).