igb: Fix string truncation warnings in igb_set_fw_version

Commit 1978d3ea ("intel: fix string truncation warnings")
fixes '-Wformat-truncation=' warnings in igb_main.c by using kasprintf.

drivers/net/ethernet/intel/igb/igb_main.c:3092:53: warning：‘%d’ directive output may be truncated writing between 1 and 5 bytes into a region of size between 1 and 13 [-Wformat-truncation=]
 3092 |                                  "%d.%d, 0x%08x, %d.%d.%d",
      |                                                     ^~
drivers/net/ethernet/intel/igb/igb_main.c:3092:34: note：directive argument in the range [0, 65535]
 3092 |                                  "%d.%d, 0x%08x, %d.%d.%d",
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/intel/igb/igb_main.c:3092:34: note：directive argument in the range [0, 65535]
drivers/net/ethernet/intel/igb/igb_main.c:3090:25: note：‘snprintf’ output between 23 and 43 bytes into a destination of size 32

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure.

Fix this warning by using a larger space for adapter->fw_version,
and then fall back and continue to use snprintf.

Fixes: 1978d3ea ("intel: fix string truncation warnings")
Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Cc: Kunwu Chan <kunwu.chan@hotmail.com>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>