nfsd: Fix NFSD_MDS_PR_KEY on 32-bit by adding ULL postfix

On 32-bit:

    fs/nfsd/blocklayout.c: In function ‘nfsd4_block_get_device_info_scsi’:
    fs/nfsd/blocklayout.c:337: warning: integer constant is too large for ‘long’ type
    fs/nfsd/blocklayout.c:344: warning: integer constant is too large for ‘long’ type
    fs/nfsd/blocklayout.c: In function ‘nfsd4_scsi_fence_client’:
    fs/nfsd/blocklayout.c:385: warning: integer constant is too large for ‘long’ type

Add the missing "ULL" postfix to 64-bit constant NFSD_MDS_PR_KEY to fix
this.

Fixes: f99d4fbd ("nfsd: add SCSI layout support")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>