Remove regcache_descr fields sizeof_raw_register_status and sizeof_cooked_register_status

Remove regcache_descr fields sizeof_raw_register_status and sizeof_cooked_register_status

struct regcache_descr has two fields sizeof_raw_register_status
and sizeof_cooked_register_status, but they equal to nr_cooked_registers
and nr_raw_registers respectively, so this patch removes them.

gdb:

2017-11-02  Yao Qi  <yao.qi@linaro.org>

	* regcache.c (struct regcache_descr) <sizeof_raw_register_status>:
	Remove.
	<sizeof_cooked_register_status>: Remove.
	(init_regcache_descr): Update.
	(regcache::regcache): Use nr_cooked_registers and nr_raw_registers.
	(regcache::save): Likewise.
	(regcache::dump): Likewise.