rom.sh: remove unnecessary check

the cbfs function will call cbfstool, which will perform
the same check, and the same error condition would cause
the same exit behaviour in lbmk. the error message would
also provide output that is just as useful for debugging.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/rom.sh

@@ -259,7 +259,6 @@ add_uboot()
 	[ "$payload_uboot_amd64" = "y" ] && \
 	    ubootelf="$ubdir/u-boot-x86-with-spl.bin" # EFI-compatible
 
-	[ -f "$ubootelf" ] || $err "cb/$ubtarget: Can't find u-boot"
 	cbfs "$tmprom" "$ubootelf" "$ubpath" $ubcbfsargs
 	[ "$payload_seabios" = "y" ] || cprom; :
 }