test: Move some test drivers into their own file

At present several test drivers are part of the test file itself. Some of
these are useful for of-platdata tests. Separate them out so we can use
them for other things also.

A few adjustments are needed so this driver can build for sandbox_spl as
well.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 947bd3a..d737203 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -67,6 +67,7 @@
 obj-$(CONFIG_SYS_DPAA_QBMAN) += fsl_portals.o
 obj-$(CONFIG_TEGRA186_BPMP) += tegra186_bpmp.o
 obj-$(CONFIG_TEGRA_CAR) += tegra_car.o
+obj-$(CONFIG_TEST_DRV) += test_drv.o
 obj-$(CONFIG_TWL4030_LED) += twl4030_led.o
 obj-$(CONFIG_VEXPRESS_CONFIG) += vexpress_config.o
 obj-$(CONFIG_WINBOND_W83627) += winbond_w83627.o