Fix a bug where a reference to the DT was erroneously obtained through
&self (instead of self) which was causing Fdt::totalsize() to return a
wrong value (probably read from the stack where &self pointed to), in
turn making Fdt::as_slice() return the wrong region of memory. This UB
seems to have consistently resulted in fdt.totalsize() == 0 i.e.
fdt.as_slice() == &[] and has gone unnoticed until now.
Avoid casting pointers with as in as_{mut_,}ptr().
Bug: 280425124
Test: atest MicrodroidHostTests
Change-Id: Ie31f6c6f19e756ee843d1fd2f11f106590e99395
Merged-In: Ie31f6c6f19e756ee843d1fd2f11f106590e99395
68980bee75