hw/block/nvme: fix potential overflow

hw/block/nvme: fix potential overflow

page_size is a uint32_t, and zasl is a uint8_t, so the expression
`page_size << zasl` is done using 32-bit arithmetic and might overflow.
Since we then compare this against a 64 bit data_size value, Coverity
complains that we might overflow unintentionally. An MDTS/ZASL value in
excess of 4GiB is probably impractical, but it is not entirely
unrealistic, so add a cast such that we handle that case properly.

Fixes: 578d914b263c ("hw/block/nvme: align zoned.zasl with mdts")
Fixes: CID 1450756
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>