regulator: bd9576: Constify struct linear_range

'struct linear_range' are not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increase overall security.

This is also more consistent with the other struct linear_range declaration
above.

On a x86_64, with allmodconfig, as an example:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  20767	   4544	      0	  25311	   62df	drivers/regulator/bd9576-regulator.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  21023	   4288	      0	  25311	   62df	drivers/regulator/bd9576-regulator.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://patch.msgid.link/a4e37991ea7b47145ab033128c8dd49f73a983e6.1722949232.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Mark Brown <broonie@kernel.org>