include: configs: at91/sam: remove stray #ifdef/#else

With the commit that moves the BOOTCOMMAND to Kconfig:

970bf860 ("Convert CONFIG_USE_BOOTCOMMAND et al to Kconfig")

some stray ifdefs have been left in the header files which
are now useless.
Clean up the include files to remove these lines.

Fixes: 970bf860 ("Convert CONFIG_USE_BOOTCOMMAND et al to Kconfig")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>