kernel: bump 5.15 to 5.15.173
Removed because they are upstream:
generic/backport-5.15/430-v6.3-udf-Allocate-name-buffer-in-directory-iterator-on-he.patch
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.15.y&id=
5ea4b73e268bf9e1d26271943f2f7c4517253395
generic/backport-5.15/431-v6.3-udf-Avoid-directory-type-conversion-failure-due-to-E.patch
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.15.y&id=
8b1d55e43cee631e142d46ee94c91ccd894341e9
Link: https://github.com/openwrt/openwrt/pull/16999
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>