bcm27xx: fix malformed upstream arm64 DT patch

bcm27xx: fix malformed upstream arm64 DT patch

This patch was causing buildbot issues when copying arm64 DT files since
bcm283x-rpi-csi1-2lane.dtsi and bcm283x-rpi-lan7515.dtsi were linked to
"../../../../arm/boot/dts/" instead of "../../../../arm/boot/dts/broadcom".
These files aren't needed, so let's remove them instead of fixing them.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/15762
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>