vpx_dec_fuzzer: Remove fmemopen dependency
vpx_dec_fuzzer: Remove fmemopen dependency

fmemopen is not preferred during fuzzing.
Removed all file operations.

Removed need for allocating a different input buffer.
data buffer is appropriately incremented and passed directly to decoder
This will also test input being sent in an unaligned buffer to the library.

Removed read_frame function and did the required parsing inline.

Change-Id: I32829b0149dba9339f2e8bb4c0249a4987a630c7

webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx