disk: part_efi: fix regression due to incorrect buffer usage

disk: part_efi: fix regression due to incorrect buffer usage

Commit deb5ca80275e8cfa74d5680b41204e08a095eca5 "disk: part_efi: fix
**pgpt_pte == NULL" modified the code to pass "&gpt_head" to
is_gpt_valid() rather than the previous "gpt_head". However, gpt_head
is a pointer to the buffer, not the actual buffer, since it was allocated
using ALLOC_CACHE_ALIGN_BUFFER. This caused is_gpt_valid() to read the
disk block onto the stack rather than into the buffer, causing the
code to fail.

This change reverts that portion of the commit mentioned above.

Signed-off-by: Stephen Warren <[email protected]>
Acked-by: Doug Anderson <[email protected]>
Tested-by: Simon Glass <[email protected]>
Acked-by: Mike Frysinger <[email protected]>
Tested-by: Anton Staaf <[email protected]>