libpng: upgrade 1.6.51 -> 1.6.52

libpng: upgrade 1.6.51 -> 1.6.52

Handles CVE-2025-66293

>From Release Notes [1]:
  Fixed CVE-2025-66293 (high severity):
    Out-of-bounds read in `png_image_read_composite`.
    (Reported by flyfish101 <flyfish101@users.noreply.github.com>.)
  Fixed the Paeth filter handling in the RISC-V RVV implementation.
    (Reported by Filip Wasil; fixed by Liang Junzhao.)
  Improved the performance of the RISC-V RVV implementation.
    (Contributed by Liang Junzhao.)
  Added allocation failure fuzzing to oss-fuzz.
    (Contributed by Philippe Antoine.)

[1] https://github.com/pnggroup/libpng/blob/v1.6.52/CHANGES#L6307-L6316

Signed-off-by: Peter Marko <peter.marko@siemens.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>