dtrace: Add pid provider to the build for powerpc

The fasttrap pid provider has been in place for a long time, but stopped
getting built by efe88d92da in preparation for 64-bit atomics.  32-bit
emulation of 64-bit atomics was added in 9aafc7c05.

MFC after:	3 weeks

sys/modules/dtrace/Makefile

@@ -20,6 +20,9 @@ SUBDIR+=	fasttrap fbt systrace_linux
 SUBDIR+=	systrace_linux32
 SUBDIR+=	kinst
 .endif
+.if ${MACHINE_CPUARCH} == "powerpc"
+SUBDIR+=	fasttrap fbt
+.endif
 .if ${MACHINE_CPUARCH} == "amd64" || \
     ${MACHINE_CPUARCH} == "aarch64" || \
     ${MACHINE_ARCH} == "powerpc64"
@@ -27,7 +30,6 @@ SUBDIR+=	systrace_freebsd32
 .endif
 .if ${MACHINE_CPUARCH} == "aarch64" || \
     ${MACHINE_CPUARCH} == "arm" || \
-    ${MACHINE_CPUARCH} == "powerpc" || \
     ${MACHINE_CPUARCH} == "riscv"
 SUBDIR+=	fbt
 .endif