jffs2: nodemgmt: fix kernel-doc comments

Update the end of one sentence where a comment was truncated. (dwmw2)

Fix a bunch of kernel-doc warnings:

nodemgmt.c:72: warning: Function parameter or member 'sumsize' not described in 'jffs2_do_reserve_space'
nodemgmt.c:72: warning: expecting prototype for jffs2_reserve_space(). Prototype was for jffs2_do_reserve_space() instead
nodemgmt.c:76: warning: Function parameter or member 'sumsize' not described in 'jffs2_reserve_space'
nodemgmt.c:76: warning: No description found for return value of 'jffs2_reserve_space'
nodemgmt.c:503: warning: Function parameter or member 'ofs' not described in 'jffs2_add_physical_node_ref'
nodemgmt.c:503: warning: Function parameter or member 'ic' not described in 'jffs2_add_physical_node_ref'
nodemgmt.c:503: warning: Excess function parameter 'new' description in 'jffs2_add_physical_node_ref'
nodemgmt.c:503: warning: No description found for return value of 'jffs2_add_physical_node_ref'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: linux-mtd@lists.infradead.org
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Richard Weinberger <richard@nod.at>