rpm-postinst: remove un-needed RDEPENDS on base-files

rpm-postinst: remove un-needed RDEPENDS on base-files

This was transferred un-intentionally when we split the rpm code,
the base-files then layed down additional files (specificaly /etc/mtab)
in the initramfs image and caused problems for the installer code.

Removing the RDEPENDS will fix the image generation issue and thus
the installer, so we will need to revert a previous patch that attempted
to fix the earlier issue #4229.

[YOCTO #4504]
[YOCTO #4229]

(From OE-Core rev: 6861eb34e903c5ddf491eca04011b2219fe14267)

Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>