busybox-init: drop pivot_root

From the help, pivot_root is intended for use with initrd on Linux 2.4.
Initramfs and Linux >=2.6 is supposed to use switch_root instead.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>

packages/sysutils/busybox/config/busybox-init.conf

@@ -1,7 +1,7 @@
 #
 # Automatically generated make config: don't edit
 # Busybox version: 1.32.1
-# Thu Feb  4 21:25:28 2021
+# Fri Feb  5 01:01:29 2021
 #
 CONFIG_HAVE_DOT_CONFIG=y
 
@@ -669,7 +669,7 @@ CONFIG_MOUNTPOINT=y
 # CONFIG_NOLOGIN is not set
 # CONFIG_NOLOGIN_DEPENDENCIES is not set
 # CONFIG_NSENTER is not set
-CONFIG_PIVOT_ROOT=y
+# CONFIG_PIVOT_ROOT is not set
 # CONFIG_RDATE is not set
 # CONFIG_RDEV is not set
 # CONFIG_READPROFILE is not set