Fix link errors for AV1 on x86/x86-64

Manual modification of generated header files.
This changes #defines so that x86_64 uses C instead of not-compiled
SSE routines; removes code that references not-compiled SSE2 routines
on x86; for both, fixes references to MMX state reseting.

Since these changes are within generated files as part of pulling from
upstream, we expect to overwrite them the next time we re-generate those
files.

Bug: 122391143
Test: build for x86 and x86_64
Change-Id: I96bc34032d26e7172b01ff5e72723c00b0c7fdfb