CODING_STYLE: explicitly allow braceless 'else if'

CODING_STYLE: explicitly allow braceless 'else if'

It's already allowed by the example; there are about 1800 instances in the
tree; and disallowing it would lead to

    if (a) {
        ...
    } else {
        if (b) {
            ...
        } else {
            if (c) {
                ...
            } else {
                if (d) {
                    ...
                } else {
                    ...
                }
            }
        }
    }

instead of

    if (a) {
        ...
    } else if (b) {
        ...
    } else if (c) {
        ...
    } else if (d) {
        ...
    } else {
        ...
    }

which is more readable.

Acked-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>