utils/genrandconfig: improve ARM trusted firmware fixup

Improve commit 541e794a959914d1189570c3674908eb5db08ce8 by adding a
custom case to make sure that a random configuration with an empty
platform for arm-trusted-firmware doesn't fail:

make_helpers/plat_helpers.mk:15: *** "Error: Unknown platform. Please use PLAT=<platform name> to specify the platform".  Stop.

Fixes:
 - http://autobuild.buildroot.org/results/1b67220008223d1bcbe70b76d643f9d04362ba6b

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit d3e029575c29cad2ba40cce7bf4270a28b83870e)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

utils/genrandconfig

@@ -427,6 +427,10 @@ def fixup_config(sysinfo, configfile):
         configlines.remove('BR2_KERNEL_HEADERS_CUSTOM_TARBALL=y\n')
         configlines.remove('BR2_KERNEL_HEADERS_CUSTOM_TARBALL_LOCATION=""\n')
 
+    if 'BR2_TARGET_ARM_TRUSTED_FIRMWARE=y\n' in configlines and \
+       'BR2_TARGET_ARM_TRUSTED_FIRMWARE_PLATFORM=""\n' in configlines:
+        return False;
+
     if 'BR2_TARGET_ARM_TRUSTED_FIRMWARE=y\n' in configlines and \
        'BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_VERSION=y\n' in configlines and \
        'BR2_TARGET_ARM_TRUSTED_FIRMWARE_CUSTOM_VERSION_VALUE=""\n' in configlines: