Fixed bug in padding.
Fixed bug in padding.

Instead of adding up to 4 zero bits, it added at least 4 zero bits.
See https://www.thonky.com/qr-code-tutorial/data-encoding under
"Add a Terminator of 0s if Necessary"

Also fix typo in variable name.

trezor/trezor-qrenc,trezor/trezor-qrenc