egl/wayland: ensure correct buffer size on swrast too

Fixes: 903ad594 ("wayland/egl: Ensure correct buffer size when allocating")
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
23 jobs for !1902 with egl-wl-swrast-fix in 13 minutes and 53 seconds (queued for 5 seconds)
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