${WARNOVERRIDE} was misspelled as ${WARNOVVERIDE}, which caused a shell
syntax error in certain paths of the script execution.

Fixes: 46dff8d7 ("scripts: merge_config: Add option to suppress warning on overrides")
Signed-off-by: NMirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Reviewed-by: NMark Brown <broonie@kernel.org>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>