Linux 6.6 compat: fix configure error with clang

[kentdobias]

With Linux v6.6.x and clang 16, a configure step fails on a warning that later results in an error while building, due to 'ts' being uninitialized. Add a trivial initialization to silence the warning.

Motivation and Context

This change resolves this issue regarding compilation of zfs for the Linux 6.6 series with clang.

Description

An uninitialized variable in the configure script causes a test regarding inode-times to fail where it shouldn't, which later causes the build to fail. This change trivially initializes that variable to silence the warning that leads to this problem.

How Has This Been Tested?

I applied this patch and was able to successfully build the kernel with zfs, where before it was failing.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.