crypto: qat - fix warning on adf_pfvf_pf_proto.c

Building the QAT driver with -Wmaybe-uninitialized triggers warnings in
qat_common/adf_pfvf_pf_proto.c. Specifically, the variables blk_type,
blk_byte, and byte_max may be used uninitialized in handle_blkmsg_req():

make M=drivers/crypto/intel/qat W=1 C=2 "KCFLAGS=-Werror" \
KBUILD_CFLAGS_KERNEL=-Wmaybe-uninitialized \
CFLAGS_MODULE=-Wmaybe-uninitialized

...
warning: ‘byte_max’ may be used uninitialized [-Wmaybe-uninitialized]
warning: ‘blk_type’ may be used uninitialized [-Wmaybe-uninitialized]
warning: ‘blk_byte’ may be used uninitialized [-Wmaybe-uninitialized]

Although the caller of handle_blkmsg_req() always provides a req.type
that is handled by the switch, the compiler cannot guarantee this.

Add a default case to the switch statement to handle an invalid req.type.

Fixes: 673184a2a58f ("crypto: qat - introduce support for PFVF block messages")
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Ahsan Atta <ahsan.atta@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>