generic: backport net-dsa-realtek use devm_mutex_init for locks

generic: backport net-dsa-realtek use devm_mutex_init for locks

Backport four upstream commits that convert mutex_init() calls to
devm_mutex_init() in the Realtek DSA driver family. With
CONFIG_DEBUG_MUTEXES enabled, mutex_destroy() must be called before a
mutex is discarded; using the devm variant handles this cleanup
automatically and avoids leaking a warning on driver removal/failure.

Added patches (applied to both backport-6.12 and backport-6.18):
- 944-01: net: dsa: realtek: rtl8365mb: use devm_mutex_init for mib_lock
- 944-02: net: dsa: realtek: use devm_mutex_init for regmap lock
- 944-03: net: dsa: realtek: use devm_mutex_init for vlan_lock
- 944-04: net: dsa: realtek: use devm_mutex_init for l2_lock

Signed-off-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>
Link: https://github.com/openwrt/openwrt/pull/24486
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>