board/ti/am62x-sk: move post-build.sh to board/ti/common/am6xx

The patch makes it clear that the moved script can be used by the
am6{2,4}x platforms.

Reviewed-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Romain Naour <romain.naour@smile.fr>

configs/ti_am62x_sk_defconfig

@@ -2,7 +2,7 @@ BR2_aarch64=y
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_6=y
 BR2_GLOBAL_PATCH_DIR="board/ti/am62x-sk/patches"
 BR2_DOWNLOAD_FORCE_CHECK_HASHES=y
-BR2_ROOTFS_POST_BUILD_SCRIPT="board/ti/am62x-sk/post-build.sh"
+BR2_ROOTFS_POST_BUILD_SCRIPT="board/ti/common/am6xx/post-build.sh"
 BR2_ROOTFS_POST_BUILD_SCRIPT_ARGS="-c ttyS2,115200n8 -d k3-am625-sk.dtb -l am62x-sk-buildroot -r /dev/mmcblk1p2 -x earlycon=ns16550a,mmio32,0x02800000"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
 BR2_ROOTFS_POST_IMAGE_SCRIPT_ARGS="-c board/ti/am62x-sk/genimage.cfg"