bcc/tools/fileslower: Attach to vfs_read after failing to attach __vfs_read
bcc/tools/fileslower: Attach to vfs_read after failing to attach __vfs_read

__vfs_read has been removed since kernel v5.8-rc5
775802c0571f ("fs: remove __vfs_read"). Then try vfs_read instead.

Signed-off-by: He Zhe <a3bd65281adbcf25519dae3b8193f9759d7ff222@windriver.com>

tuxology/bcc,tuxology/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc,iovisor/bcc,tuxology/bcc,brendangregg/bcc,brendangregg/bcc,tuxology/bcc,brendangregg/bcc,tuxology/bcc,brendangregg/bcc,iovisor/bcc,brendangregg/bcc