s390x: fix clang 11 warnings in cpu_models.c

s390x: fix clang 11 warnings in cpu_models.c

There are void * pointers that get casted to enums, in cpu_models.c
Such casts can result in a small integer type and are caught as
warnings with clang, starting with version 11:

Clang 11 finds a bunch of spots in the code that trigger this new warnings:

../qemu-base/target/s390x/cpu_models.c:985:21: error: cast to smaller integer type 'S390Feat' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390Feat feat = (S390Feat) opaque;
                    ^~~~~~~~~~~~~~~~~
../qemu-base/target/s390x/cpu_models.c:1002:21: error: cast to smaller integer type 'S390Feat' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390Feat feat = (S390Feat) opaque;
                    ^~~~~~~~~~~~~~~~~
../qemu-base/target/s390x/cpu_models.c:1036:27: error: cast to smaller integer type 'S390FeatGroup' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390FeatGroup group = (S390FeatGroup) opaque;
                          ^~~~~~~~~~~~~~~~~~~~~~
../qemu-base/target/s390x/cpu_models.c:1057:27: error: cast to smaller integer type 'S390FeatGroup' from 'void *' [-Werror,-Wvoid-pointer-to-enum-cast]
    S390FeatGroup group = (S390FeatGroup) opaque;
                          ^~~~~~~~~~~~~~~~~~~~~~
4 errors generated.

Avoid this warning by casting the pointer to uintptr_t first.

Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com>
Message-Id: <20201105221905.1350-3-dbuono@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>