x86: efi-x86_app: Update MAINTAINERS

Previous rename of efi-x86 target missed the MAINTAINERS update,
which caused the buildman warnings:

  WARNING: no status info for 'efi-x86_app'
  WARNING: no maintainers for 'efi-x86_app'

This updates the board MAINTAINERS to reflect the up-to-date info.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed