[media] docs-rst: simplify c:type: cross references

Instead of using c:type:`struct foo <foo>`, use:
	struct c:type:`foo`

This patch was generated via this shell script:

	for i in `find Documentation/media -type f`; do perl -ne 'if (m/\:c\:type\:\`struct\s+(\S+)\s*\<(\S+)\>\`/) { $s=$1; $r=$2; if ($s eq $r) { s/\:c\:type\:\`struct\s+(\S+)\s*\<(\S+)\>\`/struct :c:type:`$2`/; s/struct\s+struct/struct/;  s/(struct\s+\:c\:type\:\`\S+\`)\s+structure/$1/;  }} print $_' <$i >a && mv a $i; done

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>