x86/entry/vdso: Add vdso2c to .gitignore

The commit

  a76108d0 ("x86/entry/vdso: Move vdso2c to arch/x86/tools")

moved vdso2c to arch/x86/tools/ and commit

  93d73005 ("x86/entry/vdso: Rename vdso_image_* to vdso*_image")

renamed .so files but also dropped vdso2c from
arch/x86/entry/vdso/.gitignore.

It should've moved it to arch/x86/tools/.gitignore instead.

Do that.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260127221633.GAaXk5QcG8ILa1VWYR@fat_crate.local