DPE: Fix bitwise operation order in convert_to_ascii_hex

In C, the & operator has a lower precedence than bit shifts.
As a result, the mask for the high nibble is shifted instead
of the result of the bitwise AND. Fix this by adding parentheses.

Signed-off-by: Aditya Deshpande <aditya.deshpande@arm.com>
Change-Id: I55cc0791c3d2142bb8a8c2b156787e1ee8dbaa1e
diff --git a/partitions/dice_protection_environment/dpe_certificate.c b/partitions/dice_protection_environment/dpe_certificate.c
index f95702e..94ca197 100644
--- a/partitions/dice_protection_environment/dpe_certificate.c
+++ b/partitions/dice_protection_environment/dpe_certificate.c
@@ -29,7 +29,7 @@
     size_t out_pos = 0;
 
     for (in_pos = 0; in_pos < in_size && out_pos < out_size; in_pos++) {
-        out[out_pos++] = hex_table[(in[in_pos] & 0xF0 >> 4)];
+        out[out_pos++] = hex_table[(in[in_pos] & 0xF0) >> 4];
         out[out_pos++] = hex_table[in[in_pos] & 0x0F];
     }
 }