lte_sample_rates = True does not return radix-2 rates

[matth3wh]

srsRAN_4G/lib/src/phy/common/phy_common.c

Line 353 in ec29b0c

return 1536;

The function srsran_symbol_sz_power2 seems to return a non-radix-2 symbol size when 75 PRB is the input. This creates an issue with using a USRP N310 at 75 PRB, as the N310 needs Radix-2 rates (#171).

I believe simply changing the above line to return=1024 should fix the issue.