RP2040: Fix inaccuracy in delay_100ns()

The delay was really just 40 ns before.
Still enough to satisfy SCSI timing, but since this is used only for
command & other slow transfers, it makes sense to leave some margin.

lib/ZuluSCSI_platform_RP2040/ZuluSCSI_platform.h

@@ -45,7 +45,7 @@ static inline void delay_ns(unsigned long ns)
 // Approximate fast delay
 static inline void delay_100ns()
 {
-    asm volatile ("nop \n nop \n nop \n nop \n nop");
+    asm volatile ("nop \n nop \n nop \n nop \n nop \n nop \n nop \n nop \n nop \n nop \n nop");
 }
 
 // Initialize SD card and GPIO configuration