dbg: replace zm_uart_send with A_PRINTF

theoretically zm_uart_send should work like snprintf with
limiting size of the string. Practically, string size was ignored:
zm_uart_send(x, y) A_PUTS(x)

As result, terminal was trashed with not printable chars.
We replacing it with A_PRINTF.

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
dbg: remove db_dump_memory

db_dump_memory is not correctly. Also functionality of this caommand
overlap with db_cmd_memdump. There place only for one of this functions :)

This patch fix a build warning too.

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
dbg: remove empty functions

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
dbg: make local functions static

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
dbg: remove dead code

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>