kdbus: Translate new u64-based kernel_cap_t to u32-based kdbus_caps

kdbus: Translate new u64-based kernel_cap_t to u32-based kdbus_caps

Using kernel_cap_t in kdbus_meta_caps changes the alignment of userland
facing structures which breaks userland code trying to parse the structure
sent in kdbus header. Translate kernel_cap_t to u32 similarly to what's
done in capget(2).

Change-Id: I8c21746dca2972cbc0ad48dfea4dba2216c0669c
Ref: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f122a08b197d076ccf136c73fae0146875812a88
Fixes: e59920a ("kdbus: use u64 capability for v6.3 or later version")
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>