csky: Use va_pa_offset instead of phys_offset

The name of phys_offset is so common for global export and it may
conflict with some local name. So change phys_offset to va_pa_offset
which also used by riscv.

Also use __pa() and __va() instead of using phys_offset directly.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Arnd Bergmann <arnd@arndb.de>

arch/csky/kernel/entry.S

@@ -40,7 +40,7 @@ ENTRY(csky_\name)
 	WR_MCIR	a2
 #endif
 	bclri   r6, 0
-	lrw	a2, phys_offset
+	lrw	a2, va_pa_offset
 	ld.w	a2, (a2, 0)
 	subu	r6, a2
 	bseti	r6, 31
@@ -51,7 +51,7 @@ ENTRY(csky_\name)
 	addu    r6, a2
 	ldw     r6, (r6)
 
-	lrw	a2, phys_offset
+	lrw	a2, va_pa_offset
 	ld.w	a2, (a2, 0)
 	subu	r6, a2
 	bseti	r6, 31