Remove unneeded quote escaping inside ``

Double quotes don't need to be escaped inside Bash command substitution.
Also switch to the more modern $(), easier for humans to parse (and which happens to be less forgiving about such extra backslash escapes).

Signed-off-by: Quentin Minster <quentin@minster.io>

Author: laomaiweng

defaults/initrd.scripts

@@ -894,7 +894,7 @@ cmdline_hwopts() {
 				MY_HWOPTS="${MY_HWOPTS} $x"
 			elif [ "${y}" = "no${x}" ]
 			then
-				MY_HWOPTS="`echo ${MY_HWOPTS} | sed -e \"s/${x}//g\" -`"
+				MY_HWOPTS="$(echo ${MY_HWOPTS} | sed -e "s/${x}//g" -)"
 			fi
 			if [ "$(echo ${y} | cut -b -7)" = "keymap=" ]
 			then