cxgb4: Update firmware to revision 1.26.6.0

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>

WHENCE

@@ -578,14 +578,14 @@ Driver: cxgb4 - Chelsio Terminator 4/5/6 1/10/25/40/100G Ethernet adapter
 
 File: cxgb4/t4fw-1.14.4.0.bin
 File: cxgb4/t4fw-1.15.37.0.bin
-File: cxgb4/t4fw-1.26.4.0.bin
+File: cxgb4/t4fw-1.26.6.0.bin
-Link: cxgb4/t4fw.bin -> t4fw-1.26.4.0.bin
+Link: cxgb4/t4fw.bin -> t4fw-1.26.6.0.bin
 File: cxgb4/t5fw-1.14.4.0.bin
 File: cxgb4/t5fw-1.15.37.0.bin
-File: cxgb4/t5fw-1.26.4.0.bin
+File: cxgb4/t5fw-1.26.6.0.bin
-Link: cxgb4/t5fw.bin -> t5fw-1.26.4.0.bin
+Link: cxgb4/t5fw.bin -> t5fw-1.26.6.0.bin
-File: cxgb4/t6fw-1.26.4.0.bin
+File: cxgb4/t6fw-1.26.6.0.bin
-Link: cxgb4/t6fw.bin -> t6fw-1.26.4.0.bin
+Link: cxgb4/t6fw.bin -> t6fw-1.26.6.0.bin
 File: cxgb4/aq1202_fw.cld
 File: cxgb4/bcm8483.bin
 File: cxgb4/configs/t4-config-default.txt