xen: Fix XEN_EXTRAVERSION after 4.19-rc1

Currently, the banner reports:

  __  __            _  _    _  ___   ___
  \ \/ /___ _ __   | || |  / |/ _ \ / _ \    _ __ ___
   \  // _ \ '_ \  | || |_ | | (_) | | | |__| '__/ __|
   /  \  __/ | | | |__   _|| |\__, | |_| |__| | | (__
  /_/\_\___|_| |_|    |_|(_)_|  /_/ \___/   |_|  \___|

and xl reports:

  # xl info xen_version
  4.190-rc

Drop the 0, which is in line with how we annotate RCs elsewhere.

Fixes: 4a73eb4c20 ("Update Xen version to 4.19-rc")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-Acked-By: Oleksii Kurochko <oleksii.kurochko@gmail.com>

xen/Makefile

@@ -6,7 +6,7 @@ this-makefile := $(call lastword,$(MAKEFILE_LIST))
 # All other places this is stored (eg. compile.h) should be autogenerated.
 export XEN_VERSION       = 4
 export XEN_SUBVERSION    = 19
-export XEN_EXTRAVERSION ?= 0-rc$(XEN_VENDORVERSION)
+export XEN_EXTRAVERSION ?= -rc$(XEN_VENDORVERSION)
 export XEN_FULLVERSION   = $(XEN_VERSION).$(XEN_SUBVERSION)$(XEN_EXTRAVERSION)
 -include xen-version