BaseTools:ECC need to handle lower case 'static'

BaseTools:ECC need to handle lower case 'static'

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=1778

We are going to add keyword (lower case) 'static' for functions and global
variables which are not referenced outside their current C file.

However, the ECC tool only recognizes upper case 'STATIC' at this moment.
This will lead to issue reports for new codes that follow the above coding
style.

This patch is going to handle lower case 'static'

Cc: Liming Gao <liming.gao@intel.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>