LU-11770 osd-ldiskfs: clean up inline macro usage

LU-11770 osd-ldiskfs: clean up inline macro usage

Remove inline macro usage as much as possible in the osd-ldiskfs
code, per Linux and Lustre code style.  Balance start/end braces
for functions to keep syntax highlighting working properly.

Change the autoconf macros to be checking for the new structure
fields instead of the old fields, and add compat macros for older
kernels so that they can later be removed without code churn.

Remove direct inode->truncate() usage and autoconf check, since
ldiskfs_truncate() has been exported since at least RHEL6.3.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ifc3187275c1841918228fac2368b18a9fa89a47d
Reviewed-on: https://review.whamcloud.com/33841
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>