[armel/marvell] Disable HW_RANDOM as no HWRNG drivers are usable here

We were building the omap-rng driver, because the same block is used
on some recent Marvell chips and HW_RANDOM_OMAP is enabled by default
if ARCH_MVEBU is enabled.

We were also building virtio-rng, but there isn't (so far as I know)
any publicly available emulation of the ARMv5 Marvell chips.

As we're about to include HWRNG drivers to the installer, disable the
whole subsystem for armel/marvell to avoid adding useless drivers.

debian/changelog

@@ -799,6 +799,7 @@ linux (4.19.34-1) UNRELEASED; urgency=medium
   * [armhf,arm64] Revert "net: stmmac: Send TSO packets always from Queue 0"
   * [riscv64] linux-image-dbg: Include vdso debug symbols
   * [ia64] linux-image: Recommend grub-efi-ia64 instead of (removed) elilo
+  * [armel/marvell] Disable HW_RANDOM as no HWRNG drivers are usable here
 
   [ YunQiang Su ]
   * [mips*r6] Re-enable CONFIG_JUMP_LABEL, which has been fixed in upstream.

debian/config/armel/config.marvell

@@ -202,6 +202,11 @@ CONFIG_BT_HCIBPA10X=m
 CONFIG_BT_HCIBFUSB=m
 CONFIG_BT_HCIVHCI=m
 
+##
+## file: drivers/char/hw_random/Kconfig
+##
+# CONFIG_HW_RANDOM is not set
+
 ##
 ## file: drivers/connector/Kconfig
 ##