cifs: Remove duplicate struct reparse_symlink_data and SYMLINK_FLAG_RELATIVE

In file common/smb2pdu.h is defined struct reparse_symlink_data_buffer
which is same as struct reparse_symlink_data and is used in the whole code.
So remove duplicate struct reparse_symlink_data from client/cifspdu.h.

In file common/smb2pdu.h is defined also SYMLINK_FLAG_RELATIVE constant, so
remove duplication from client/cifspdu.h.

Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>