powerpc/vas: Include linux/types.h in uapi/asm/vas-api.h

powerpc/vas: Include linux/types.h in uapi/asm/vas-api.h

allyesconfig fails with:
  ./usr/include/asm/vas-api.h:15:2: error: unknown type name '__u32'
     15 |  __u32 version;
        |  ^~~~~
  ./usr/include/asm/vas-api.h:16:2: error: unknown type name '__s16'
     16 |  __s16 vas_id; /* specific instance of vas or -1 for default */
        |  ^~~~~
  ./usr/include/asm/vas-api.h:17:2: error: unknown type name '__u16'
     17 |  __u16 reserved1;
        |  ^~~~~
  ./usr/include/asm/vas-api.h:18:2: error: unknown type name '__u64'
     18 |  __u64 flags; /* Future use */
        |  ^~~~~
  ./usr/include/asm/vas-api.h:19:2: error: unknown type name '__u64'
     19 |  __u64 reserved2[6];
        |  ^~~~~

uapi headers should be self contained, so add an include of
linux/types.h.

Fixes: 45f25a79fe50 ("powerpc/vas: Define VAS_TX_WIN_OPEN ioctl API")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Haren Myneni <haren@linux.ibm.com>
[mpe: Flesh out change log from linux-next error report]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200422154129.11f988fd@canb.auug.org.au