util/format: Fix clamping to 32bit integers.

util/format: Fix clamping to 32bit integers.

Use clamping constants that guarantee no integer overflows.

As spotted by Chris Forbes.

This causes the code to change as:

-         value |= (uint32_t)CLAMP(src[0], 0.0f, 4294967295.0f);
+         value |= (uint32_t)CLAMP(src[0], 0.0f, 4294967040.0f);

-         value |= (uint32_t)((int32_t)CLAMP(src[0], -2147483648.0f, 2147483647.0f));
+         value |= (uint32_t)((int32_t)CLAMP(src[0], -2147483648.0f, 2147483520.0f));

Reviewed-by: Roland Scheidegger <sroland@vmware.com>