LU-13344 osd-ldiskfs: timespec64 is broken

LU-13344 osd-ldiskfs: timespec64 is broken

Linux commit v5.5-rc1-6-gba70609d5ec6 removed timespec64_trunc
which was being used to determine if inode times were timespec64
Change this test to work with kernels without timespec64_truc

Linux-commit: ba70609d5ec664a8f36ba1c857fcd97a478adf79

Linux commit v5.4-rc3-21-g933f1c1e0b75 renamed h_buffer_credits
to h_total_credits

Add a configure test to determine and #define to handle this
change of name.

Linux-commit: 933f1c1e0b75bbc29730eef07c9e196c6dfd37e5

Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I112da3385e5f33cbee8aadfd3efdbb4b3b823819
Reviewed-on: https://review.whamcloud.com/38314
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>