Doc: Debug document added (gdb)
Doc: Debug document added (gdb)

Add first version of a document that explains how to debug OP-TEE. In
this version debugging with gdb is explained. For future revisions we
would like to include JTAG debugging etc. for other targets.

Signed-off-by: Joakim Bech <741f90e2a7f4d9afbad8bd50be20560f4cf38962@linaro.org>
Tested-by: Joakim Bech <741f90e2a7f4d9afbad8bd50be20560f4cf38962@linaro.org> (QEMU)
Reviewed-by: Pascal Brand <0b55292d2562685bad4ce52d64f802e8f1cd299e@linaro.org>

chshxi1989/optee_os,matt2048/optee_os,Microsoft/optee_os,cedric-chaumont-st-dev/optee_os,chshxi1989/optee_os,BreezeWu/optee_os,Microsoft/optee_os,matt2048/optee_os,BreezeWu/optee_os,pascal-brand-st-dev/optee_os,BreezeWu/optee_os,cedric-chaumont-st-dev/optee_os,pascal-brand-st-dev/optee_os,matt2048/optee_os,chshxi1989/optee_os,matt2048/optee_os,BreezeWu/optee_os,chshxi1989/optee_os,BreezeWu/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,cedric-chaumont-st-dev/optee_os,cedric-chaumont-st-dev/optee_os,chshxi1989/optee_os,Microsoft/optee_os,Microsoft/optee_os,pascal-brand-st-dev/optee_os