nouveau: honor fread return value in the nouveau_compiler

nouveau: honor fread return value in the nouveau_compiler

There is little point of continuing if fread returns zero, as it
indicates that either the file is empty or cannot be read from.
Bail out if fread returns zero after closing the file.

Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>