phy: broadcom: Kconfig: Fix PHY_BRCM_USB config option

The previous commit 4b402fa8 ("phy: phy-brcm-usb: support PHY on
the BCM4908") added a second "default" line for ARCH_BCM_4908 above
the original "default" line for ARCH_BRCMSTB. When two "default"
lines are used, only the first is used and this change stopped
the PHY_BRCM_USB option for being enabled for ARCH_BRCMSTB.
The fix is to use one "default line with "||".

Fixes: 4b402fa8 ("phy: phy-brcm-usb: support PHY on the BCM4908")
Signed-off-by: Al Cooper <alcooperx@gmail.com>
Acked-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20211201180653.35097-4-alcooperx@gmail.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/broadcom/Kconfig

@@ -97,8 +97,7 @@ config PHY_BRCM_USB
 	depends on OF
 	select GENERIC_PHY
 	select SOC_BRCMSTB if ARCH_BRCMSTB
-	default ARCH_BCM4908
-	default ARCH_BRCMSTB
+	default ARCH_BCM4908 || ARCH_BRCMSTB
 	help
 	  Enable this to support the Broadcom STB USB PHY.
 	  This driver is required by the USB XHCI, EHCI and OHCI