Add definitions of SYSCFG registers and memory remap function
In debug_uart.c, only include softirq.h with CONFIG_KDB
Correct the type(uint32_t --> size_t) of "size" in function queue_init.
Loader merged with f9 kernel(containing user space)

It is WIP version of loader.  The following are future work.
   1. Merged build system with f9 kernel.
   2. Remove duplicated files in loader(xxx_ld.c).  They are just
      for easy building.
Add Loader option in kconfig

It could build f9 which is self booting or booted by loader.
Add boolean type.
Remove duplicated program in loader and share with kernel
Delete files which loader no longer uses.
Move elf files to its folder and rename the loader main file(main.c --> loader.c).
Remove confused include paths in Makefile.

The include paths shoule be declared clearly and can not interfer
previous used include paths.
Add strip command.
Merge loader building rule into main building system
Remove unused elf64
Rename f9_nor.ld to f9_flash.ld
Rename the suffix of loader object file. (.lo --> .loader.o)
Remove obsolete Makefile
loader: remove unused elf64
loader: fix silly typo in linker script
loader: simplify configuration level
loader: Remove unused elf64 headers