arm64: Fix COMPAT_FREEBSD32.
The ENTRY() macro was modified by commit 28d94520 to add an optional NOP instruction at the beginning of the function. It is of course an arm64 instruction, so unsuitable for the 32bits sigcode. So just use EENTRY() instead for aarch32_sigcode. This should fix receiving signals when running 32bits binaries on FreeBSD/arm64. MFC After: 1 week