Because file_name and phba->ModelName are both declared a size 80 bytes,
the extra ".grp" file extension could cause an overflow into file_name.

Define a ELX_FW_NAME_SIZE macro with value 84.  84 incorporates the 4 extra
characters from ".grp".  file_name is changed to be declared as a char and
initialized to zeros i.e. null chars.
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Link: https://lore.kernel.org/r/20231031191224.150862-3-justintee8345@gmail.comReviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>