[binutils-gdb] Remove regcache_cooked_read_part

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 73bb0000525a67694c1e8921e7c34ee0d985787e ***

Author: Simon Marchi <simon.marchi@ericsson.com>
Branch: master
Commit: 73bb0000525a67694c1e8921e7c34ee0d985787e

Remove regcache_cooked_read_part

Remove regcache_cooked_read_part, update callers to use
readable_regcache::cooked_read_part.

gdb/ChangeLog:

	* regcache.h (regcache_cooked_read_part): Remove, update callers
	to use readable_regcache::cooked_read_part.
	* regcache.c (regcache_cooked_read_part): Remove.