frameworks/native: Increase EGL blob cache size limits

Increase the size of the EGL Blob Cache to 2MB and the key size to 4K.
This helps improve the performance of OpenGL apps, especially Open GLESv1.1
apps whose shaders are generated on the fly.

This was backported from CM10

Change-Id: Iec5ddaa206a65c66f8150ec82e78fa9934b06e25