tpm: fix alignment issues

tpm: fix alignment issues

The new tpm-crb-test fails on sparc host:

TEST: tests/tpm-crb-test... (pid=230409)
  /i386/tpm-crb/test:
Broken pipe
FAIL
GTester: last random seed: R02S29cea50247fe1efa59ee885a26d51a85
(pid=230423)
FAIL: tests/tpm-crb-test

and generates a new clang sanitizer runtime warning:

/home/petmay01/linaro/qemu-for-merges/hw/tpm/tpm_util.h:36:24: runtime
error: load of misaligned address 0x7fdc24c00002 for type 'const
uint32_t' (aka 'const unsigned int'), which requires 4 byte alignment
0x7fdc24c00002: note: pointer points here
<memory cannot be printed>

The sparc architecture does not allow misaligned loads and will
segfault if you try them.  For example, this function:

static inline uint32_t tpm_cmd_get_size(const void *b)
{
    return be32_to_cpu(*(const uint32_t *)(b + 2));
}

Should read,
    return ldl_be_p(b + 2);

As a general rule you can't take an arbitrary pointer into a byte
buffer and try to interpret it as a structure or a pointer to a
larger-than-bytesize-data simply by casting the pointer.

Use this clean up as an opportunity to remove unnecessary temporary
buffers and casts.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>