s390: remove gcc version check (4.3 or newer)

git commit cafa0010

 ("Raise the minimum required gcc version to 4.6")
raised the minimum gcc version to 4.6. Therefore remove the s390 specific
gcc 4.3 version check, which wasn't sufficient anyway.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>