i2cdetect: don't die on addresses already in use by drivers

i2cdetect: don't die on addresses already in use by drivers

We can't use i2c_set_slave_addr() in i2cdetect, as we have to check for
EBUSY after calling ioctl(I2C_SLAVE) and print 'UU' on busy addresses
instead of bailing-out.

While we're at it: reorder definitions of local vars in i2cdetect_main().

function                                             old     new   delta
i2cdetect_main                                       703     744     +41
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 41/0)               Total: 41 bytes
   text	   data	    bss	    dec	    hex	filename
 826097	   4164	   9584	 839845	  cd0a5	busybox_old
 826145	   4164	   9584	 839893	  cd0d5	busybox_unstripped

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>