secagentd: bpf: read __i_mtime in newer kernel
Starts from Linux kernel v6.7-rc1, commit 12cd4402365 ("fs: rename inode i_atime and i_mtime fields"), the field name changed.
Read from the new field if the kernel supports.
Based on I925ca4cfbbe4ffd05f7d7522fe32ccd61c8137ec
TEST=KernelCI build for corsola (mt8186)
Signed-off-by: Arnaud Ferraris arnaud.ferraris@collabora.corp-partner.google.com