[media] max2175: remove an useless comparision

load is an unsigned integer. So, it is always bigger or equal
to zero, as reported by gcc:

	drivers/media/i2c/max2175.c: In function 'max2175_refout_load_to_bits':
	drivers/media/i2c/max2175.c:1272:11: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
	  if (load >= 0 && load <= 40)
	           ^~

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>