soft_i2c.c compiler/linker error

This patch fix the compiler/linker errors

common/cmd_i2c.c:1252: undefined reference to `i2c_get_bus_speed'
common/cmd_i2c.c:1256: undefined reference to `i2c_set_bus_speed'

if board use CONFIG_I2C_CMD_TREE and CONFIG_I2C_MULTI_BUS is not
uesd/undef (wrong define order)

and

removes additional empty lines

Signed-off-by: Jens Scharsig <esw@bus-elektronik.de>