at91: configs: Drop duplication of defconfig macros

'commit a9221f3e ("at91, omap2plus: configs: migrate CONFIG_ENV_ to defconfigs")'
migrated CONFIG_ENV_ macros to defconfigs but did not remove the
identical redefinition of these macros in include/configs/.

Since the duplicated macros have the same value as the ones in defconfigs,
no "redefined" warnings were raised. Remove duplicated macros for all
sama5 and sam9x5ek boards.

While verifying that the removal of the macros from include/configs did
not change the same macros in defconfigs, overwrite the old defconfig by
saving them with the output from "make arch=ARM savedefconfig". This
resulted in the movement of some macros in the defconfig files.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>