arch: Fix duplicates in Kconfig for parisc and sparc

Fix duplicates for sparc and parisc. This was due these following commits.

1. commit 4c97a0c8 ("arch: define CPU_BIG_ENDIAN for all fixed big
   endian archs")
2. commit 97d9f969 ("arch/sparc: Define config parameter
   CPU_BIG_ENDIAN")
3. commit 74ad3d28

 ("parisc: Define CONFIG_CPU_BIG_ENDIAN")

Remove duplicates.

Signed-off-by: Babu Moger <babu.moger@oracle.com>
Signed-off-by: Helge Deller <deller@gmx.de>