configs/imx6q-sabresd: Drop the 'quad' notation

Now that SPL is supported a single image can run on the different
variants of imx6 sabresd boards: imx6q, imx6dl and imx6qp.

So drop the 'quad' prefix from defconfig, directory and readme file
to make it generic.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

configs/imx6-sabresd_defconfig

@@ -0,0 +1,38 @@
+BR2_arm=y
+BR2_cortex_a9=y
+BR2_ARM_ENABLE_NEON=y
+BR2_ARM_ENABLE_VFP=y
+BR2_ARM_FPU_VFPV3=y
+
+# Linux headers same as kernel, a 4.13 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_13=y
+
+# System
+BR2_TARGET_GENERIC_GETTY_PORT="ttymxc0"
+
+# required tools to create the SD card image
+BR2_PACKAGE_HOST_DOSFSTOOLS=y
+BR2_PACKAGE_HOST_GENIMAGE=y
+BR2_PACKAGE_HOST_MTOOLS=y
+
+# Filesystem
+BR2_ROOTFS_POST_IMAGE_SCRIPT="board/freescale/common/imx/post-image.sh"
+BR2_TARGET_ROOTFS_EXT2=y
+BR2_TARGET_ROOTFS_EXT2_4=y
+
+# Bootloader
+BR2_TARGET_UBOOT=y
+BR2_TARGET_UBOOT_BOARDNAME="mx6sabresd"
+BR2_TARGET_UBOOT_CUSTOM_VERSION=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2017.07"
+BR2_TARGET_UBOOT_FORMAT_IMG=y
+BR2_TARGET_UBOOT_SPL=y
+BR2_TARGET_UBOOT_SPL_NAME="SPL"
+
+# Kernel
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.13"
+BR2_LINUX_KERNEL_DEFCONFIG="imx_v6_v7"
+BR2_LINUX_KERNEL_DTS_SUPPORT=y
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx6q-sabresd imx6dl-sabresd imx6qp-sabresd"