YH820/YH92X: Improve some keymaps for plugins.

Change-Id: Ib598737327043809f60127f7c538f2d45ddabb87
Rockboy plugin: remove second keymap definition for the Iriver H10, added in
594b6e2 (FS#10251).

Change-Id: I652545c812a8bd4d5d1be5f200fce9c97733b636
YH820/YH92X: Add missing StdMenu action.

Change-Id: Ife5be1b6427724b5c231e0035aca44373adb0e40
Manual for the Samsung YH920/YH925.

Change-Id: I2db0023cae585e9c9517da9ed2e9de6195081ce2
Pegbox: use the same keymap for Samsung YH820 and YH920.

Keymap for the YH820 fits much better for the YH920 anyway.

Change-Id: I54d7f3be9dfaf689e76c73d39da4649395e912a1
Manual for the Samsung YH820.

Change-Id: I1c760b4846963f39b9df60413ffbb9f95dc0e0fb