powerpc/Kconfig: Make TM select VSX and VMX

There are no processors in existence that have TM but no VMX or VSX.  So let's
makes CONFIG_PPC_TRANSACTIONAL_MEM select both CONFIG_VSX and CONFIG_ALTIVEC.
This makes the code a lot simpler by removing the need for a bunch of #ifdefs.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>