PM: hibernate: Fix some kernel-doc comments

Add parameter description in alloc_rtree_node()  kernel-doc
comment and fix several inconsistent function name descriptions.

Remove some warnings found by running scripts/kernel-doc,
which is caused by using 'make W=1'.

kernel/power/snapshot.c:438: warning: Function parameter or member
'gfp_mask' not described in 'alloc_rtree_node'
kernel/power/snapshot.c:438: warning: Function parameter or member
'safe_needed' not described in 'alloc_rtree_node'
kernel/power/snapshot.c:438: warning: Function parameter or member 'ca'
not described in 'alloc_rtree_node'
kernel/power/snapshot.c:438: warning: Function parameter or member
'list' not described in 'alloc_rtree_node'
kernel/power/snapshot.c:916: warning: expecting prototype for
memory_bm_rtree_next_pfn(). Prototype was for memory_bm_next_pfn()
instead
kernel/power/snapshot.c:1947: warning: expecting prototype for
alloc_highmem_image_pages(). Prototype was for alloc_highmem_pages()
instead
kernel/power/snapshot.c:2230: warning: expecting prototype for load
header(). Prototype was for load_header() instead

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
[ rjw: Comment adjustments to avoid line breaks ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>