command: Remove the cmd_tbl_t typedef

We should not use typedefs in U-Boot. They cannot be used as forward
declarations which means that header files must include the full header to
access them.

Drop the typedef and rename the struct to remove the _s suffix which is
now not useful.

This requires quite a few header-file additions.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd: add exception command

The 'exception' command allows to test exception handling.

This implementation supports ARM, x86, RISC-V and the following exceptions:
* 'breakpoint' - prefetch abort exception (ARM 32bit only)
* 'unaligned' - data abort exception (ARM only)
* 'undefined' - undefined instruction exception

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

cmd: add exception command

The 'exception' command allows to test exception handling.

This implementation supports ARM, x86, RISC-V and the following exceptions:
* 'breakpoint' - prefetch abort exception (ARM 32bit only)
* 'unaligned' - data abort exception (ARM only)
* 'undefined' - undefined instruction exception

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>