boot/shim: fix build issues with gcc 9.x

boot/shim: fix build issues with gcc 9.x

Backport a set of upstream patches to fix:

MokManager.c: In function ‘write_back_mok_list’:
MokManager.c:1081:19: error: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
 1081 |   if (CompareGuid(&(list[i].Type), &X509_GUID) == 0)
      |                   ^~~~~~~~~~~~~~~
MokManager.c:1103:19: error: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
 1103 |   if (CompareGuid(&(list[i].Type), &X509_GUID) == 0) {
      |                   ^~~~~~~~~~~~~~~
MokManager.c: In function ‘delete_cert’:
MokManager.c:1144:19: error: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
 1144 |   if (CompareGuid(&(mok[i].Type), &X509_GUID) != 0)
      |                   ^~~~~~~~~~~~~~
MokManager.c: In function ‘delete_hash_in_list’:
MokManager.c:1195:20: error: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
 1195 |   if ((CompareGuid(&(mok[i].Type), &Type) != 0) ||
      |                    ^~~~~~~~~~~~~~
MokManager.c: In function ‘delete_keys’:
MokManager.c:1359:19: error: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Werror=address-of-packed-member]
 1359 |   if (CompareGuid(&(del_key[i].Type), &X509_GUID) == 0) {
      |                   ^~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[1]: *** [<builtin>: MokManager.o] Error 1

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>