drm/etnaviv: Improve VA, PA, SIZE alignment checking

Alignment checking is only needed to be done in the upper caller function.
If those address and sizes are able to pass the check, it will certainly
pass the same test in the etnaviv_context_unmap() function. We don't need
examine it more than once.

Remove redundant alignment tests, move the those useless to upper caller
function.

Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>