[arch][arm64] move the exception table after .text.boot
[arch][arm64] move the exception table after .text.boot

This puts _start at the beginning of a flattened binary, which
makes it slightly easier to read, at the expense of adding a bit
more padding to get the exception table (.text.boot.vectab) aligned
on a 4K boundary.

travisg/lk,minglun-tsai/lk,ErikCorryGoogle/lk,M1cha/lk,nvll/lk,srodrig1/lk,M1cha/lk,hollanderic/lkstuff,M1cha/lk,GCrean/lk,travisg/lk,littlekernel/lk,sndnvaps/lk,skabet/lk,ErikCorryGoogle/lk,minglun-tsai/lk,GCrean/lk,hollanderic/lkstuff,skabet/lk,skabet/lk,ErikCorryGoogle/lk,grub4android/lk,minglun-tsai/lk,nvll/lk,minglun-tsai/lk,grub4android/lk,srodrig1/lk,grub4android/lk,travisg/lk,GCrean/lk,littlekernel/lk,grub4android/lk,hollanderic/lkstuff,skabet/lk,M1cha/lk,travisg/lk,sndnvaps/lk,srodrig1/lk,nvll/lk,GCrean/lk,GCrean/lk,srodrig1/lk,hollanderic/lkstuff,littlekernel/lk,M1cha/lk,sndnvaps/lk,skabet/lk,sndnvaps/lk,sndnvaps/lk,nvll/lk,ErikCorryGoogle/lk,nvll/lk,srodrig1/lk,grub4android/lk,littlekernel/lk