meta: stop using "virtual/" in RPROVIDES and RDEPENDS

Fixes [YOCTO #14538]

Recipes shouldn't use the "virtual/" string in RPROVIDES and RDEPENDS.

That's confusing because "virtual/" has no special meaning in
RPROVIDES and RDEPENDS (unlike in PROVIDES and DEPENDS).

Instead, using "virtual-" instead of "virtual/"
as already done in the glibc recipe.

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>