Add parentheses to ALLOC_ALIGN_BUFFER macro's

Without those it's very easy to make mistakes when for instance
the 'size' field is more than just a constant.

Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Anton Staaf <robotboy@chromium.org>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>