LTP i2c test: added min/max test and fixes (refs #34386)

Adaptions for SANVITO bit tests:
* changed order of registers access for @i2c@ read/write test
** previous order (write A, read A, write B, read B) doesn't make any sense
** using (write A, write B, read A, read B), now, to also verifiy proper register addressing (no changes to test-parameters necessary for this modification)
* added new read min/max-test to @i2c@ tool
** reads register A and compares result against min/max values, than are specified via new @-n (miN)@ and @-x (maX)@ parameters (no writes are performed, when these parameters are specified and reg-B parameters are ignored).
** can interpret read results of 8, 16, 24 or 32 bit length (with already existing @-l@ parameter
** can interpret read data as either big-endian (default) or little-endian value (using new @-e@ parameter)
* Used new @i2c@ read min/max-tests in SANVITO @bit@ script to implement proper ambient and proximity tests

Change-Id: I68c43f8c7d5a787113ef790a83d3348dcfc2e992
Reviewed-on: http://gfweb/gerrit/488