scripts/gdb: fix lx-device-list-bus and lx-device-list-class

After the conversion to bus_to_subsys() and class_to_subsys(), the gdb
scripts listing the system buses and classes respectively was broken, fix
those by returning the subsys_priv pointer and have the various caller
de-reference either the 'bus' or 'class' structure members accordingly.

Link: https://lkml.kernel.org/r/20231130043317.174188-1-florian.fainelli@broadcom.com
Fixes: 7b884b7f24b4 ("driver core: class.c: convert to only use class_to_subsys")
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Tested-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/gdb: add helpers to find and list devices

Add helper commands and functions for finding pointers to struct device
by enumerating linux device bus/class infrastructure. This can be used
to fetch subsystem and driver-specific structs:

(gdb) p *$container_of($lx_device_find_by_class_name("net", "eth0"), "struct net_device", "dev")
(gdb) p *$container_of($lx_device_find_by_bus_name("i2c", "0-004b"), "struct i2c_client", "dev")
(gdb) p *(struct imx_port*)$lx_device_find_by_class_name("tty", "ttymxc1")->parent->driver_data

Several generic "lx-device-list" functions are included to enumerate
devices by bus and class:

(gdb) lx-device-list-bus usb
(gdb) lx-device-list-class
(gdb) lx-device-list-tree &platform_bus

Similar information is available in /sys but pointer values are
deliberately hidden.

Link: http://lkml.kernel.org/r/c948628041311cbf1b9b4cff3dda7d2073cb3eaa.1561492937.git.leonard.crestez@nxp.com
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>