vtenc: should support GLMemory

Submitted by Nick Kallen

Link to original bug (#778496)

Description

Currently vtenc caps disallow GLMemory. However, having tested this on iOS and reviewed the code, it actually works using GLMemory. Since the underlying pixel buffer is always a core media buffer,

pbuf = gst_core_media_buffer_get_pixel_buffer (frame->input_buffer);  

this statement is valid whether the input_buffer's pixel buffer is GL buffer or not.

Therefore, just changing the static caps works.

Version: 1.11.1