gve: Modify rx_buf_alloc_fail counter centrally and closer to failure

Previously, each caller of gve_rx_alloc_buffer had to increase counter
 and as a result one caller was not tracking those failure. Increasing
 counters at a common location now so callers don't have to duplicate
 code or miss counter management.

Signed-off-by: Ankit Garg <nktgrg@google.com>
Link: https://lore.kernel.org/r/20240124205435.1021490-1-nktgrg@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>