Bluetooth: tester: Increase the adv buf size to consider the extend adv

[Description]
Device hang is observed when LE Scan
[Root Cause]
For le_ext_adv_report, Data[i] of one adv report is 0-229,
for the adv_buf of saving, it just is 73 bytes, so sometimes
the bytes of adv report is more than the adv_buf, resulted hang
[Fix]
consider the le ext adv case.
[Testing]
After modified, Device hang is not observed after stress
testing with LE Scan

Signed-off-by: Guotao Zhang <guotao.zhang@nxp.com>