imx6: rename target to 'imx'

This is first step in migrating to a generic i.MX target which in the
next steps will also get divided into arch-specific subtargets.

In the result, this will make it possible to support, within a single
target, also other modern NXP i.MX families, like the i.MX 7, i.MX 8
or recently introduced i.MX 9.

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

target/linux/imx/image/bootscript-solidrun_cubox-i

@@ -0,0 +1,31 @@
+echo "CuBox OpenWrt Boot script"
+
+# Set console variable for both UART and HDMI
+setenv console console=ttymxc0,115200 video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24,bpp=32
+
+# Find correct dtb
+if test ${board_rev} = MX6DL; then
+	setenv fdt_soc_type imx6dl;
+elif test ${board_rev} = MX6Q; then
+	setenv fdt_soc_type imx6q;
+fi
+if test ${board_name} = CUBOXI; then
+	setenv fdt_name ${fdt_soc_type}-cubox-i.dtb;
+elif test ${board_name} = HUMMINGBOARD; then
+	setenv fdt_name ${fdt_soc_type}-hummingboard.dtb;
+fi
+
+# Set correct devtype and partition
+if test ${devtype} != mmc; then setenv devtype mmc; fi
+if mmc dev 0; then
+	setenv mmcdev 0
+elif mmc dev 1; then
+	setenv mmcdev 1
+fi
+
+# Boot from the SD card is supported at the moment
+setenv bootargs "${console} root=/dev/mmcblk1p2 rw rootwait"
+mmc dev ${mmcdev}
+load ${devtype} ${mmcdev}:${devplist} ${kernel_addr_r} /uImage
+load ${devtype} ${mmcdev}:${devplist} ${fdt_addr_r} /${fdt_name}
+bootz ${kernel_addr_r} - ${fdt_addr_r}