ARM: spear: remove include/mach/ subdirectory

Two of the remaining four headers are never used, the other
two are only used inside of the platform code. Move them
next to the files that include them and remove the
Makefile trick that adds the include path.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>