score/sparc: Add support for paravirtualization

Guest systems in paravirtualization environments run usually in user
mode.  Thus it is not possible to directly access the PSR and TBR
registers.  Use functions instead of inline assembler to access these
registers if RTEMS_PARAVIRT is defined.

c/src/lib/libcpu/sparc/syscall/syscall.S

@@ -83,4 +83,40 @@ SYM(sparc_syscall_exit):
 	mov	%o1, %g3	! Additional exit code 2
 	ta	0
 
+#if defined(RTEMS_PARAVIRT)
+
+        PUBLIC(_SPARC_Get_PSR)
+
+SYM(_SPARC_Get_PSR):
+
+	retl
+	 rd     %psr, %o0
+
+        PUBLIC(_SPARC_Set_PSR)
+
+SYM(_SPARC_Set_PSR):
+
+	mov     %o0, %psr
+	nop
+	nop
+	nop
+	retl
+	 nop
+
+        PUBLIC(_SPARC_Get_TBR)
+
+SYM(_SPARC_Get_TBR):
+
+	retl
+	 rd    %tbr, %o0
+
+        PUBLIC(_SPARC_Set_TBR)
+
+SYM(_SPARC_Set_TBR):
+
+	retl
+	 wr    %o0, 0, %tbr
+
+#endif /* defined(RTEMS_PARAVIRT) */
+
 /* end of file */