rigol-ds1xx2: detect Rigol DS1xx2 with upgraded bandwith

rigol-ds1xx2: detect Rigol DS1xx2 with upgraded bandwith

The bandwith in Rigol DS1xx2D/E scopes can be upgraded to 150 MHz in software.
So detect also scopes with the upgraded bandwith.

using libsigrok-0.2.1 + this change + commit da970d24ec (required for newer kernels):

[dan@eagle sigrok]$ sigrok-cli --scan -d rigol-ds1xx2 -l 5
sr: libsigrok loglevel set to 5.
sr: Sanity-checking all drivers.
sr: Sanity-checking all input modules.
sr: Sanity-checking all output modules.
srd: libsigrokdecode loglevel set to 5.
sr: hwdriver: Initializing driver 'rigol-ds1xx2'.
sr: serial: Opening serial port '/dev/usbtmc0' (flags 1).
sr: serial: Opened serial port '/dev/usbtmc0' (fd 7).
sr: serial: Wrote 5/5 bytes (fd 7).
sr: serial: Closing serial port /dev/usbtmc0 (fd 7).
sr: rigol-ds1xx2: response: /dev/usbtmc0 [Rigol Technologies,DS1152D,DS1EU150XXXXXX,00.04.01.00.02]
sr: hwdriver: Scan of 'rigol-ds1xx2' found 1 devices.
The following devices were found:
rigol-ds1xx2 - Rigol Technologies DS1152D 00.04.01.00.02 with 18 probes: CH1 CH2 D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15