coresight: configfs: Constify struct config_item_type

coresight: configfs: Constify struct config_item_type

'struct config_item_type' is not modified in this driver.

These structures are only used with config_group_init_type_name() which
takes a "const struct config_item_type *" as a 3rd argument or with
struct config_group.cg_item.ci_type which is also a "const struct
config_item_type	*".

Constifying this structure moves some data to a read-only section, so
increase overall security, especially when the structure holds some
function pointers.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
   4904	   1376	    136	   6416	   1910	drivers/hwtracing/coresight/coresight-syscfg-configfs.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
   5264	   1120	     16	   6400	   1900	drivers/hwtracing/coresight/coresight-syscfg-configfs.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/1011717e5ed35ec12113a0d8c233823e820fb524.1723368522.git.christophe.jaillet@wanadoo.fr