Issue type: Bug

[x] bug report
[ ] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[x] postgres
[ ] cockroachdb
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[x] latest
[ ] @next
[] 0.x.x (or put your version here)

Steps to reproduce or a small repository showing the problem:

class Comment {
    any: any;
    object: {[k: string]: any};
}

commentRepository.create({
    any: {
        foo: 'bar',
    },
    object: {
        foo: 'bar'
    },
});

results in:

TS2322: Type '{ foo: string; }' is not assignable to type 'DeepPartial<{}>[] | ReadonlyArray<DeepPartial<{}>> | DeepPartial | undefined'.   Type '{ foo: string; }' is not assignable to type 'undefined'.

TS2322: Type '{ foo: string; }' is not assignable to type 'DeepPartial<{ [k: string]: any; }>'.   Property 'foo' is incompatible with index signature.     Type 'string' is not assignable to type 'DeepPartial<{}>[] | ReadonlyArray<DeepPartial<{}>> | DeepPartial | undefined'.

I'll create tests and a PR.