ext2fs: Migrate to modern uintXX_t from u_intXX_t

[fsu]

Summary

https://cgit.freebsd.org/src/commit/?id=d69d55f78b93f1b639df61a7470b053614548fbb for ext2fs

Test Plan

Tested using https://github.com/thedrgreenthumb/Jenkins/tree/master/Target/ext2fs_test_all testcases.
The i386 compilation passed successfully.

[pfg]

Thank you for doing this! When moving from the linux headers we moved from the linux types to the standard C types but some leftover BSD types were still being used. These changes actually fix some hidden bugs.