auto/config: scope ubuntu:desktop-preinstalled:raspi image options

When desktop-preinstalled image options were added in
38157b3748, for the raspi subarch, the
options listed there were not scoped for raspi subarch. This results
in those options getting also applied for the HYPERV
ubuntu:desktop-preinstalled image.

Thus scope the newly added options under raspi subarch case only.

(cherry picked from commit 1c7d688319)

LP: #1901846

live-build/auto/config

@@ -604,14 +604,16 @@ case $PROJECT in
 				add_task install minimal standard ubuntu-desktop
 				if [ "$SUBARCH" = "raspi" ]; then
 					add_task install ubuntu-desktop-raspi
-				fi
 					# XXX: Are those actually needed? I see we use those for ubuntu-cpc, which is the project
 					#  for existing raspi preinstalled images
+					# XXX: I would prefer to use --hdd-label=desktop-rootfs like 040-hyperv-desktop-images.binary
 					OPTS="${OPTS:+$OPTS }--initramfs=none"
 					OPTS="${OPTS:+$OPTS }--system=normal"
 					OPTS="${OPTS:+$OPTS }--hdd-label=cloudimg-rootfs"
 					OPTS="${OPTS:+$OPTS }--ext-resize-blocks=536870912 --ext-block-size=4096"
 					OPTS="${OPTS:+$OPTS }--ext-fudge-factor=15"
+				fi
+				## Otherwise HYPERV image options.... *crickets* see the hyperv hook
 				;;
 
 			*)