dm: sysreset: Add a Kconfig option for the 'reset' command

dm: sysreset: Add a Kconfig option for the 'reset' command

sysreset uclass driver provides an implementation of 'reset'
command using the sysreset_ APIs unconditionally. It also
supports the 'poweroff' command using the sysreset_ APIs,
but under a Kconfig option CONFIG_SYSRESET_CMD_POWEROFF.

Let's do the same for the 'reset' command, by introducing a
new Kconfig option CONFIG_SYSRESET_CMD_RESET, and set it to
on by default, to allow a board that don't have a sysreset
reset driver yet, but have a sysreset poweroff driver to
compile without any issue.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>