scripts: gdb: vfs: support external dentry names

scripts: gdb: vfs: support external dentry names

d_shortname of struct dentry only reserves D_NAME_INLINE_LEN characters
and contains garbage for longer names.  Use d_name instead, which always
references the valid name.

Link: https://lore.kernel.org/all/20250525213709.878287-2-illia@yshyn.com/
Link: https://lkml.kernel.org/r/20250629003811.2420418-1-illia@yshyn.com
Fixes: 79300ac805b6 ("scripts/gdb: fix dentry_name() lookup")
Signed-off-by: Illia Ostapyshyn <illia@yshyn.com>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>