asf test failure on mips64 (big endian)

[neheb]

Describe the bug

test fails

To Reproduce

Steps to reproduce the behavior:

/home/mangix/devstuff/exiv2/c/bin/exiv2 -Pkycvt /home/mangix/devstuff/exiv2/test/data/sample_960x540.asf
Exiv2 exception in print action for file /home/mangix/devstuff/exiv2/test/data/sample_960x540.asf:
/home/mangix/devstuff/exiv2/test/data/sample_960x540.asf: The file contains data of an unknown image type

Expected behavior

succeeds

Desktop (please complete the following information):

• OS and version: gcc230 on cfarm
• Exiv2 version and source: master
• Compiler and version: Debian 10 8.3
• Compilation mode and/or compiler flags: regular

Additional context

mips64 is big endian so that may be the issue

ping @mohamedchebbii