The elf_fpregset_t type relied on an empty struct in the asm/user.h, but
the transition to asm-generic/user.h dropped that empty struct. Rather
than restore this useless struct, define the only user (elf_fpregset_t)
as an empty struct itself. This fixes building when ELF dump support is
enabled.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>