[musl][bootloader] Use compiler-provided standard headers

<stdalign.h>, <stdarg.h>, <stdbool.h>, <stddef.h>, <stdint.h>
are all provided by the compiler and should not be replaced here.

The bootloader code's local versions were sloppy in what names
got defined where, so the code needed some #include additions
and type adjustments.

TC-32 #done

Change-Id: Ib24ba7b5072e99ec9302a6994d63ad5e16233151

[bootloader][magenta] move efi headers to shared location

Change-Id: I2851899efe8f0e1121170c08aa8d56c8112e7835