megasas: fix mapped frame size

megasas: fix mapped frame size

the current value of 1024 bytes (16 * MFI_FRAME_SIZE) we map is not enough to hold
the maximum number of scatter gather elements we advertise. We actually need a
maximum of 2048 bytes. This is 128 max sg elements * 16 bytes (sizeof (union mfi_sgl)).

Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-Id: <20190404121015.28634-1-pl@kamp.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 2e56fbc87f6ec3cd56c37b01d313abd502b80d61)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>