config: Enable USB Keyboard suuport on RPi4 32 bit

Supporting USB keyboards out of the box is both handy for development
and production. Notably if u-boot is used to boot into GRUB. This patch
adds USB keyboard support for 32 bit RPi4 config.

Signed-off-by: Matthias Brugger <mbrugger@suse.com>

configs/rpi_4_32b_defconfig

@@ -42,6 +42,7 @@ CONFIG_DM_USB=y
 CONFIG_DM_USB_GADGET=y
 CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_XHCI_PCI=y
+CONFIG_USB_KEYBOARD=y
 CONFIG_USB_GADGET=y
 CONFIG_USB_GADGET_MANUFACTURER="FSL"
 CONFIG_USB_GADGET_VENDOR_NUM=0x0525