x86: hevcdsp: use compilation-time-fixed constant

The stride for some buffers is known.
Reviewed-by: Mickaël Raulet <mraulet@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/x86/hevc_mc.asm

@@ -1211,7 +1211,7 @@ cglobal hevc_put_hevc_uni_w%1_%2, 6, 6, 7, dst, dststride, src, srcstride, heigh
 %endif
     PEL_%2STORE%1   dstq, m0, m1
     add             dstq, dststrideq             ; dst += dststride
-    lea             srcq, [srcq+2*srcstrideq]      ; src += srcstride
+    add             srcq, 2*MAX_PB_SIZE          ; src += srcstride
     dec          heightd                         ; cmp height
     jnz               .loop                      ; height loop
     RET
@@ -1282,7 +1282,7 @@ cglobal hevc_put_hevc_bi_w%1_%2, 5, 7, 10, dst, dststride, src, srcstride, src2,
 %endif
     PEL_%2STORE%1   dstq, m0, m1
     add             dstq, dststrideq             ; dst += dststride
-    lea             srcq, [srcq+2*srcstrideq]      ; src += srcstride
+    add             srcq, 2*MAX_PB_SIZE          ; src += srcstride
     add            src2q, 2*MAX_PB_SIZE          ; src2 += srcstride
     dec              r6d                         ; cmp height
     jnz               .loop                      ; height loop