llvmpipe: fix overflow bug in total texture size computation

llvmpipe: fix overflow bug in total texture size computation

v2: use uint64_t for the total_size variable, per Jose.

Also add two earlier checks for exceeding the max texture size.
For example a 1K^3 RGBA volume would overflow the lpr->image_stride
variable.

Use simple algebra to avoid overflow in intermediate values.
So instead of "x * y > z" use "x > z / y".

This should work if we happen to be on a platform that doesn't have
64-bit types.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>