mei: Avoid the use of one-element arrays

mei: Avoid the use of one-element arrays

One-element arrays are being deprecated[1]. Replace the one-element
arrays with a simple value type u8 reserved, once this is just a
placeholder for alignment.

Also, while there, use the preferred form for passing a size of a struct.
The alternative form where struct name is spelled out hurts readability
and introduces an opportunity for a bug when the variable type is changed
but the corresponding sizeof that is passed as argument is not.

[1] https://github.com/KSPP/linux/issues/79

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200714214516.GA1040@embeddedor
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>