xmc4xxx: Integrate build of erase check code

xmc4xxx: Integrate build of erase check code

Instead of pointing to the assembler sources in a comment and
inline-commenting the THUMB bytecode, place the hex array alongside the
assembler sources and include it via preprocessor.

Originally inspired by a typo in the file path during driver development,
but it also facilitates making changes to the assembler sources.

A Makefile is provided to help automate updating the bytecode. It is not
integrated with the automake system to avoid forcing an ARM cross-compiler
onto every user, i.e. after modifying the sources they need to be rebuilt
in that directory before building the usual way. ARM_CROSS_COMPILE= can
be passed on the make command line to deal with native ARM toolchains
or with varying prefixes of cross-toolchains.

Change-Id: I00ceb980a68c8554a180dd13719ac77b677a8bcd
Signed-off-by: Andreas Färber <afaerber@suse.de>
Reviewed-on: http://openocd.zylin.com/3133
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>