ARM: u300: delete remnant machine headers

Two files remain in <mach/*> for U300: timex.h and
uncompress.h. The former is done away with by using
defaults, the latter is unused in multiplatform.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>