[media] stb0899: allow minimum symbol rate of 2000000

[media] stb0899: allow minimum symbol rate of 2000000

Looks like product datasheets for tuners containing STB0899 are
suggesting specification for min. symbol rate of 2MS/s.
Some specs found here, all suggesting 2MS/s for min. symbol rate:
    Comtech DVBS2-6899
      http://comtech.sg1002.myweb.hinet.net/pdf/dvbs2-6899.pdf
    TechniSat SkyStar HD2
      http://www.scaistar.com/skystar2/skystarhd2.htm
    Azurewave AD-SP400
      http://www.pulsat.com/products/AzureWave-AD%252dSP400-High-Definition-PC-Card.html
New patch:
This makes minimum symbol rate driver capabilities on par with some
accessible datasheet specifications*, and allows tuning on linux to
transponders that have symbol rate between 2000000-5000000, too.
Patch was tested successfully on Eutelsat 16A transponders that
became reachable with it (2000000 < symbol rate < 5000000):
      * DVB/S  12507050 V  2532000 3/4
      * DVB/S2 12574000 V  4355000 3/4 8PSK
      * DVB/S  12593000 V  2500000 2/3
      * DVB/S  12596940 V  2848000 2/3
      * DVB/S  12600750 V  2500000 1/2
      * DVB/S  12675590 H  4248000 3/4
(*) Datasheet: http://comtech.sg1002.myweb.hinet.net/pdf/dvbs2-6899.pdf
        Maximum Symbol Rate
        QPSK/LDPC/PCH: 20-30Mbps
        8PSK/LDPC/BCH: 10-30Mbps
        DVB: 2-45Mbps
             ^--------- min. symbol rate

Signed-off-by: Zoran Turalija <zoran.turalija@gmail.com>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>