The sysinfo_get_str() implementation checks whether the sysinfo was even
detected. In U-Boot proper, sysinfo_detect() is not called anywhere but
on one specific board. Call sysinfo_detect() before sysinfo_get_str() to
make sure the sysinfo is detected and sysinfo_get_str() returns valid
value instead of -EPERM.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>