Add some kernel drivers

- trying to get RTC working
- also some performance optimisations

.buildbot/openwrt/build.sh

@@ -11,6 +11,9 @@
 
 set -x
 
+renice -n 19 $$
+export MAKEOPTS="-j $(nproc)"
+
 tar -xJf /Downloads/openwrt-sdk-${OPENWRT_VERSION}-*.tar.xz
 
 cp -r feed openwrt-sdk-*/
@@ -97,6 +100,15 @@ PACKAGES="kmod-nf-nathelper-extra kmod-rtc-ds1307 \
 	  wireguard-tools wget-ssl \
 	 "
 
+# kernel changes
+echo >> target/linux/bcm27xx/bcm2711/config-* << EOF
+CONFIG_RTC_DRV_PCF85063=y
+CONFIG_I2C_MUX=y
+CONFIG_I2C_MUX_PINCTRL=y
+CONFIG_REGMAP_I2C=y
+CONFIG_I2C_BCM2835=y
+EOF
+
 make image PROFILE=rpi-4 \
      PACKAGES="${PACKAGES}" DISABLED_SERVICES="dropbear" FILES="files"