Make use of 'depends on cc-option' to only display those Kconfig
options for which compiler support is available.

Add this for the MARCH and TUNE options which are the only options
which may result in compile errors if the selected architecture is not
supported by the compiler.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>