While setting up sysrq operation on the XO laptop (which lacks a SysRq
key), i realized that the documentation was quite out of date.

Change documentation of SysRq to reflect current KEY_SYSRQ value.
Signed-off-by: NPaul Fox <pgf@laptop.org>
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>