MIPS: ralink: fix USB frequency scaling

Commit 418d29c8 ("MIPS: ralink: Unify SoC id handling") was not fully
correct. The logic for the SoC check got inverted. We need to check if it
is not a MT76x8.
Signed-off-by: NJohn Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11992/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/ralink/mt7620.c

@@ -459,7 +459,7 @@ void __init ralink_clk_init(void)
 	ralink_clk_add("10000c00.uartlite", periph_rate);
 	ralink_clk_add("10180000.wmac", xtal_rate);
 
-	if (IS_ENABLED(CONFIG_USB) && is_mt76x8()) {
+	if (IS_ENABLED(CONFIG_USB) && !is_mt76x8()) {
 		/*
 		 * When the CPU goes into sleep mode, the BUS clock will be
 		 * too low for USB to function properly. Adjust the busses