Tuning gap between 325 and 350 MHz

[Kire Pudsje]

Also posted on reddit:

I measured another stick and this time I also noticed the gap between
325 and 350 MHz, as was reported earlier by Roger on reddit.
http://www.reddit.com/r/RTLSDR/comments/tftz4/some_frequency_response_measurements_potentially/

I could trace it back to the fact that the E4K_REG_SYNTH is not set
properly. I do not know why yet, but first setting a different value
from the desired one seems to fix the problem. It might be the wrong
solution for the wrong problem, but it seems to work for me.

change this line in tuner_e4k.c:448
        rc = e4k_reg_set_mask(e4k, E4K_REG_SYNTH1, 0x06, band << 1);
to:
        uint8_t tmp = e4k_reg_read(e4k, E4K_REG_SYNTH1) & ~0x06;
        tmp |= (band << 1) & 0x06;
        e4k_reg_write(e4k, E4K_REG_SYNTH1, tmp ^ 0x06);
        rc = e4k_reg_write(e4k, E4K_REG_SYNTH1, tmp);

Kire.