ARM: socfpga: Fix default mtdparts

The default mtdparts value grew a trailing zero during the Kconfig
conversion. This is because the mtdparts value in the header file
had a \0 at the end, which got misconverted into plain 0 instead of
being dropped.

Signed-off-by: Marek Vasut <marex@denx.de>
Fixes: 43ede0bc ("Kconfig: Migrate MTDIDS_DEFAULT / MTDPARTS_DEFAULT")
Reviewed-by: Tom Rini <trini@konsulko.com>