smb: client: reduce stack usage in smb2_set_ea()

Clang warns about exceeded stack frame size

  fs/smb/client/smb2ops.c:1080:1: warning: stack frame size (1432)
  exceeds limit (1024) in 'smb2_set_ea' [-Wframe-larger-than]

Fix this by allocating a structure that will hold most of the large
variables.

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>