ARM: mxs/tx28: fix odd include

arch/arm/mach-mxs/module-tx28.c includes "../devices-mx28.h". That's a
bit odd, because that header can be found in the same directory. This
only works because arch/arm/mach-mxs/include should be in the header
search path for this file. Nevertheless, this file can simply include
"device-mx28.h" (just as the four other files including that header do).

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>