output/wav: fixup coding style nits, adjust data types

output/wav: fixup coding style nits, adjust data types

Fixup unbalanced braces for more complex if statements, to better
reflect the project's official coding style.

Adjust data types in the float_to_le() routine. A float value gets
copied to a buffer of bytes (uint8_t). Don't use 'char' on the other
side of assignments, to not assume a specific width for char, and to
avoid potential signedness issues. Copy from bytes to bytes instead.