media: m88rs2000: prevent frontend crash on continuous transponder scans

commit 8272d0a0c0d374a01721e579df6e8add5577132b upstream.

Add m88rs2000_get_tune_settings, min delay of 2000 ms on symbol
rate more than 3000000 and delay of 3000ms less than this.

Adding min delay prevents crashing the frontend on continuous
transponder scans. Other dvb_frontend_tune_settings remain as default.

This makes very little time difference to good channel scans, but slows down
the set frontend where lock can never be achieved i.e. DVB-S2.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>