LU-13226 ldiskfs: Add support for SUSE 15 SP2

LU-13226 ldiskfs: Add support for SUSE 15 SP2

SUSE 15 SP2 kernel is close enough to 5.4.7+ mainline to
use the patch series directly.
Update the configure script to select it.

Test-Parameters: trivial
Cray-bug-id: LUS-8485
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I10e5b9eef6783ac153429be602bbda8d870c46d5
Reviewed-on: https://review.whamcloud.com/37490
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>