common: Fix autocompletion with CONFIG_CMDLINE_PS_SUPPORT

common: Fix autocompletion with CONFIG_CMDLINE_PS_SUPPORT

The autocompletion did not work if CONFIG_CMDLINE_PS_SUPPORT was enabled
because U-Boot was comparing the prompt string with CONFIG_SYS_PROMPT .
While this works if CONFIG_CMDLINE_PS_SUPPORT is disabled, this no longer
works if it's enabled because user can override the PS1 . Fix this by
checking prompt string against the current PS1 value.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Tom Rini <trini@konsulko.com>