pseudo: Exclude SITEINFO_BITS from checksums

pseudo: Exclude SITEINFO_BITS from checksums

We really want the same sstate checksums for pseudo-native on 32 and 64 bit platforms
but the use of SITEINFO_BITS prevents this. Since other things would change if
the bit size changes, we can safely exclude this variable and rely on others
(e.g. BUILD_ARCH included in WORKDIR) to handle this.

[YOCTO #5970]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>