arm: only compile gdb stubs when CONFIG_GDB_INFO=y
arm: only compile gdb stubs when CONFIG_GDB_INFO=y

They use data that is unavailable to the unified kernel, and are not
used anymore really. For now, only compile them when CONFIG_GDB_INFO=y,
and never enable CONFIG_GDB_INFO when building the unified kernel.

These files should go away when the unified kernel is made the only
kernel type.

Change-Id: I0a2a917dd453ecaae729125008756e0f676df16d
Signed-off-by: Benjamin Walsh <578db18f23ec223e50c404886c947386478a464e@windriver.com>

zephyrproject-rtos/zephyr,holtmann/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,runchip/zephyr-cc3220,mbolivar/zephyr,bigdinotech/zephyr,zephyriot/zephyr,ldts/zephyr,explora26/zephyr,runchip/zephyr-cc3220,zephyrproject-rtos/zephyr,finikorg/zephyr,rsalveti/zephyr,tidyjiang8/zephyr-doc,fractalclone/zephyr-riscv,bigdinotech/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,bboozzoo/zephyr,rsalveti/zephyr,rsalveti/zephyr,zephyriot/zephyr,erwango/zephyr,explora26/zephyr,runchip/zephyr-cc3200,fractalclone/zephyr-riscv,pklazy/zephyr,bigdinotech/zephyr,galak/zephyr,tidyjiang8/zephyr-doc,rsalveti/zephyr,nashif/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,fbsder/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,runchip/zephyr-cc3200,aceofall/zephyr-iotos,galak/zephyr,ldts/zephyr,erwango/zephyr,galak/zephyr,sharronliu/zephyr,aceofall/zephyr-iotos,punitvara/zephyr,nashif/zephyr,kraj/zephyr,erwango/zephyr,pklazy/zephyr,GiulianoFranchetto/zephyr,bboozzoo/zephyr,fractalclone/zephyr-riscv,tidyjiang8/zephyr-doc,finikorg/zephyr,runchip/zephyr-cc3200,ldts/zephyr,ldts/zephyr,sharronliu/zephyr,fbsder/zephyr,aceofall/zephyr-iotos,holtmann/zephyr,finikorg/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,mbolivar/zephyr,punitvara/zephyr,explora26/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,rsalveti/zephyr,GiulianoFranchetto/zephyr,sharronliu/zephyr,finikorg/zephyr,tidyjiang8/zephyr-doc,bboozzoo/zephyr,punitvara/zephyr,runchip/zephyr-cc3220,fbsder/zephyr,sharronliu/zephyr,punitvara/zephyr,punitvara/zephyr,pklazy/zephyr,zephyriot/zephyr,holtmann/zephyr,finikorg/zephyr,galak/zephyr,aceofall/zephyr-iotos,explora26/zephyr,holtmann/zephyr,erwango/zephyr,runchip/zephyr-cc3220,nashif/zephyr,pklazy/zephyr,zephyriot/zephyr,fractalclone/zephyr-riscv,nashif/zephyr,kraj/zephyr,ldts/zephyr,kraj/zephyr,runchip/zephyr-cc3220,tidyjiang8/zephyr-doc,fbsder/zephyr,erwango/zephyr,holtmann/zephyr,bigdinotech/zephyr,fractalclone/zephyr-riscv,galak/zephyr,mbolivar/zephyr,pklazy/zephyr,bboozzoo/zephyr,bboozzoo/zephyr,Vudentz/zephyr,Vudentz/zephyr,fbsder/zephyr,runchip/zephyr-cc3200,runchip/zephyr-cc3200,kraj/zephyr,bigdinotech/zephyr,sharronliu/zephyr