lms_lpf_enable issue.

[LazyDodo]

lms_lpf_enable doesn't change the enable bit unless you're changing bandwidth, when calling it after lms_lpf_disable you have to specify something other than 28Mhz for the call to work.

proposed fix

// When enabling an LPF, we must select both the module and the filter bandwidth
void lms_lpf_enable( struct bladerf *dev, lms_module_t mod, lms_bw_t bw )
{
    uint8_t reg = (mod == RX) ? 0x54 : 0x34 ;
    uint8_t data ;
    // Check to see which bandwidth we have selected
    lms_spi_read( dev, reg, &data ) ;
    data |= (1<<1) ;
    if( (lms_bw_t)(data&0x3c>>2) != bw )
    {
        data &= ~0x3c ;
        data |= (bw<<2) ;
    }
    lms_spi_write( dev, reg, data ) ;
    // Check to see if we are bypassed
    lms_spi_read( dev, reg+1, &data ) ;
    if( data&(1<<6) )
    {
        data &= ~(1<<6) ;
        lms_spi_write( dev, reg+1, data ) ;
    }
    return ;
}

[bpadalino]

Forgot to close out this issue. Whoops!