ima: Fix build failure on powerpc when TCG_IBMVTPM dependencies are not met

On powerpc we can end up with IMA=y and PPC_PSERIES=n which leads to:

 warning: (IMA) selects TCG_IBMVTPM which has unmet direct dependencies (TCG_TPM && PPC_PSERIES)
  tpm_ibmvtpm.c:(.text+0x14f3e8): undefined reference to `.plpar_hcall_norets'

I'm not sure why IMA needs to select those user-visible symbols, but if
it must then the simplest fix is to just express the proper dependencies
on the select.
Tested-by: Hon Ching (Vicky) Lo <lo1@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/ima/Kconfig

@@ -10,7 +10,7 @@ config IMA
 	select CRYPTO_HASH_INFO
 	select TCG_TPM if HAS_IOMEM && !UML
 	select TCG_TIS if TCG_TPM && X86
-	select TCG_IBMVTPM if TCG_TPM && PPC64
+	select TCG_IBMVTPM if TCG_TPM && PPC_PSERIES
 	help
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