refactor: glamor/fb: remove excess 'else' and 'struct' for code readability

[GermanAizek]

Reference to PR: #1595

[stefan11111]

@GermanAizek Usually, else if is used as an entire token, with only one level of indentation.
This is because usually else if really is a more complex switch.
If you want to add braces around it, do:

else if (foo()) {
    ...
}

Not:

else {
    if (foo())
        ...
}

At least that's the way I see it.