drivers/cmsis-dap: improve error checking

drivers/cmsis-dap: improve error checking

Check returned HID report number (or the first byte of returned
bulk packet) which should be equal to the issued command or 0xff
in case of the command is not implemented.

Fix error return paths in cmsis_dap_init() to clean up the adapter
connection.

Don't fail cmsis_dap_init() when an unimportant function fails
(for the case the adapter doesn't implement some parts of protocol).

Change-Id: Ief8382aabe9915346b2273702fb2ff17bbb5eb1b
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/6121
Tested-by: jenkins
Reviewed-by: Peter Lawrence <majbthrd@gmail.com>