man: cgset: document -R option

Document -R option. It recursively sets variable settings passed with -r
option to cgroup_path and its descendant cgroups.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>

doc/man/cgset.1

@@ -7,9 +7,9 @@
 cgset \- set the parameters of given cgroup(s)
 
 .SH SYNOPSIS
-\fBcgset\fR [\fB-b\fR] [\fB-r\fR <\fIname=value\fR>] <\fBcgroup_path\fR> ...
+\fBcgset\fR [\fB-b\fR] [\fB-R\fR] [\fB-r\fR <\fIname=value\fR>] <\fBcgroup_path\fR> ...
 .br
-\fBcgset\fR [\fB-b\fR] \fB--copy-from\fR <\fIsource_cgroup_path\fR> <\fBcgroup_path\fR> ...
+\fBcgset\fR [\fB-b\fR] [\fB-R\fR] \fB--copy-from\fR <\fIsource_cgroup_path\fR> <\fBcgroup_path\fR> ...
 
 .SH DESCRIPTION
 Set the parameters of input cgroups.
@@ -31,6 +31,11 @@ defines the name of the file to set and
 the value which should be written to that file.
 This parameter can be used multiple times.
 
+.TP
+.B -R
+recursively sets variable settings passed with -r option
+to cgroup_path and its descendant cgroups.
+
 .TP
 .B --copy-from <source_cgroup_path>
 defines the name of the cgroup whose parameters will be