boards: v2m_musca: Fix pinmux init for LEDs

Utilize CONFIG_TRUSTED_EXECUTION_NONSECURE to decide if we do pinmux.
This Kconfig option is more useful since we only set the _SECURE
version isn't set if we are ignoring the security mode feature.

Move the LED pinmux setup into the not NONSECURE case.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>