From: Gustavo A. R. Silva <gustavoars@kernel.org>
Sent: Monday, January 24, 2022 1:44 PM
 ...
Make use of the struct_size() helper instead of an open-coded version,
in order to avoid any potential type mistakes or integer overflows that,
in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
drivers/net/ethernet/microsoft/mana/gdma_main.c:677:24: warning: using
sizeof on a flexible structure
 ...
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Reviewed-by: Dexuan Cui <decui@microsoft.com>