frameworks/base: surfaceflinger: Increase min texture width limit

Increase minimum texture width limit to 480
and it should be multiple of 16 for
vertical stripes optimization.

(cherry picked from commit 624055c0927097e7db1ebc6fe025f6c66b9bca01)

Change-Id: I24d1396842590c0c39b64b80420148e26efe1772