mips: m4k alternate pracc code. Patch 3

mips: m4k alternate pracc code. Patch 3

Functions mips32_pracc_read_mem(), mips32_cp0_read() and mips32_pracc_read_regs() are now modified.
mips32_cp0_read() is very similar to mips32_read_u32() with one store access.
mips32_pracc_read_regs() is the only function that can not be executed from only one queue.
Now this function is modified to use reg8, it saves all the registers but does not restore reg8.
To remedy this, mips_ejtag_config_step() is called after mips32_save_context() in
mips_m4k_debug_entry(). Function mips_ejtag_config_step() is modified to use reg8 and
restore it from ejtag info instead of using DeSave for save/restore.

Change-Id: Icc224f6d7e41abdec94199483401cb512cc0b450
Signed-off-by: Salvador Arroyo <sarroyofdez@yahoo.es>
Reviewed-on: http://openocd.zylin.com/1195
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>