opts: Minor cleanup of ZFS options

Remove redundant CPUARCH test: we really just want a plain MACHINE_ARCH
here.

Second, always turn off LOADER_ZFS when we turn off ZFS. Not 100%
required, but we did it some places and not others. There's no current
mechanism to say that if X is disabled then X_Y must be too.

Sponsored by:		Netflix

share/mk/src.opts.mk

@@ -355,9 +355,9 @@ __DEFAULT_NO_OPTIONS+=OPENMP
 BROKEN_OPTIONS+= OFED
 .endif
 
-
+# ZFS is broken on 32-bit powerpc, but works on 64-bit
 .if ${__T} == "powerpc"
-BROKEN_OPTIONS+= ZFS
+BROKEN_OPTIONS+= ZFS LOADER_ZFS
 .endif
 
 .include <bsd.mkopt.mk>
@@ -419,6 +419,7 @@ MK_KERBEROS:=	no
 MK_KERBEROS_SUPPORT:=	no
 MK_LDNS:=	no
 MK_PKGBOOTSTRAP:=	no
+MK_LOADER_ZFS:=	no
 MK_ZFS:=	no
 .endif
 

sys/conf/kern.opts.mk

@@ -78,7 +78,8 @@ __DEFAULT_NO_OPTIONS = \
 BROKEN_OPTIONS+= INIT_ALL_ZERO
 .endif
 
-.if ${MACHINE_CPUARCH} == "powerpc" && ${MACHINE_ARCH} == "powerpc"
+# ZFS is broken on 32-bit powerpc
+.if ${MACHINE_ARCH} == "powerpc"
 BROKEN_OPTIONS+= ZFS
 .endif