Merging G2-loader

[Wolfram Sang]

Hi,

do the following assumptions and conclusions make sense?

- The Sciphone G2 is intended as a platform where we want to run L1/2/3 
natively on Linux (somewhen).

- Thus, from all the applications in osmocom-bb for the targets, we only 
need the loader to get the first bootloader onto the system (in case 
JTAG is not available or wanted)

- Being that different, it doesn't make sense to fit the 
mediatek-platform into the existing makefile-templates which build all 
applications for all boards.

I'd suggest to create a new top-level target "mtk" which only builds the 
loaders for mediatek-phones. All unneeded applications and libraries are 
skipped. A preview of a possible directory-structure to add mtk-support 
could look like this then:

.
├── board
│   ├── mediatek
│   │   ├── exceptions_redirected.S
│   │   ├── exceptions_redirect.S
│   │   ├── handlers.S
│   │   ├── header.S
│   │   ├── macros.S
│   │   ├── ram.lds
│   │   ├── start.ram.S
│   │   ├── start.rom.S
│   │   └── uart.c
│   └── mt62xx
│       └── init.c
└── include
     └── mtk
         ├── bfe.h
         ├── bpi.h
         ├── bsi.h
         ├── emi.h
         ├── mt6235.h
         ├── mt6235_sciphone_g2.h
         ├── system.h
         └── tdma_timer.h

It can be cleaned up a bit once there is a working state. Of course, a 
few modifications to makefiles are also needed. Note there is now a 
seperate uart.c in the mediatek-folder.

Any objections? Anything I missed?

Regards,

    Wolfram