Ignore asm-offsets.h for all arches.

Signed-off-by: Brian Gerst <bgerst@didntduck.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

This still leaves driver and architecture-specific subdirectories alone,
but gets rid of the bulk of the "generic" generated files that we should
ignore.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>