hw/nvme: fix number of PIDs for FDP RUH update

hw/nvme: fix number of PIDs for FDP RUH update

The number of PIDs is in the upper 16 bits of cdw10. So we need to
right-shift by 16 bits instead of only a single bit.

Fixes: 73064edfb864 ("hw/nvme: flexible data placement emulation")
Cc: qemu-stable@nongnu.org
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
(cherry picked from commit 3936bbdf9a2e9233875f850c7576c79d06add261)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>