Declare regulator_ops structures as const as it is only stored in the
ops field of a regulator_desc structure. This field is of type const, so
regulator_ops structures having this property can be made const too.

File size before: drivers/regulator/88pm8607.o
   text	   data	    bss	    dec	    hex	filename
   3466	   5488	      0	   8954	   22fa	drivers/regulator/88pm8607.o

File size after: drivers/regulator/88pm8607.o
   text	   data	    bss	    dec	    hex	filename
   3978	   4976	      0	   8954	   22fa	drivers/regulator/88pm8607.o
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>