fix: correct length being returned and used for BLE HCI reads

[deadprogram]

This PR is to address #58 along with tinygo-org/bluetooth#301 and tinygo-org/bluetooth#327

Basically, from looking at the data, I realized that the length being returned was exactly one less then the same packet from the ninafw HCI. Bumping that up allows the code to run again as expected.

[soypat]

The change is quite counterintuitive, it seems like a fix that might break in the future for packets of varying lengths since we are reading at least length+4 but returning length+1. Here's a couple of suggestions:

• Move the change to a single line, instead of returning length+1 in several places do length++ on a line before it
• You did bring an apparent mistake to my attentions, we read rounded(length+4)=roundedLength bytes from the ring buffer but return length! Maybe the reference returns the correct value here (overlooked on my part). Have you tried returning hciLength or roundedLength And seeing if it works?
• Try just adding 1 instead of 4 to the value of length to get hciLength and then repeat above step

[deadprogram]

Have you tried returning hciLength or roundedLength And seeing if it works?

Tried hciLength and that worked.

Try just adding 1 instead of 4 to the value of length to get hciLength and then repeat above step

That did NOT work.

So I will change to using hciLength since it is in fact a bit more intuitive, and did work in all my testing.

[soypat]

Thank you a million ron!