libnvme: drop the static stat buffer in nvme_verify_chr()

[prabhakarpujeri]

Problem

nvme_verify_chr() uses a static struct stat as the fstat() target, shared across all threads — concurrent resets / rescans on different transport handles race writing into it and can observe a torn st_mode. (The companion 1.x issue of returning a positive errno, linux-nvme/libnvme#1130, is already correct in this tree — it returns -errno.)

Fix

Make the buffer automatic; nothing in the function is meant to be shared or retained.

Testing

• Full meson suite green. Single-keyword change; no behavioral difference for single-threaded consumers.

[igaw]

dropped the libnvme 1 reference.

[igaw]

Thanks!