doc: add -drive rerror=,werror= to qemu --help output

These options are already documented on the man page but missing from
qemu --help.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>

qemu-options.hx

@@ -408,7 +408,8 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive,
     "-drive [file=file][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
     "       [,cyls=c,heads=h,secs=s[,trans=t]][,snapshot=on|off]\n"
     "       [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
-    "       [,serial=s][,addr=A][,id=name][,aio=threads|native]\n"
+    "       [,serial=s][,addr=A][,rerror=ignore|stop|report]\n"
+    "       [,werror=ignore|stop|report|enospc][,id=name][,aio=threads|native]\n"
     "       [,readonly=on|off][,copy-on-read=on|off]\n"
     "       [[,bps=b]|[[,bps_rd=r][,bps_wr=w]]]\n"
     "       [[,iops=i]|[[,iops_rd=r][,iops_wr=w]]]\n"