misc: Fix issues flagged by gcc 6

A few warnings (and thus errors) pop up after being added to -Wall:

1. -Wmisleading-indentation

In the auto-generated code there were instances of if/else blocks that
were not indented to gcc's liking. This is addressed by adding braces.

2. -Wshift-negative-value

gcc is clever enougn to consider ~0 a negative constant, and
rightfully complains. This is addressed by using mask() which
explicitly casts to unsigned before shifting.

That is all. Porting done.

src/arch/arm/isa/insts/neon.isa

@@ -2939,29 +2939,32 @@ let {{
     twoRegShiftInst("vrsra", "NVrsraQ", "SimdShiftAccOp", allTypes, 4, vrsraCode, True)
 
     vsriCode = '''
-        if (imm >= sizeof(Element) * 8)
+        if (imm >= sizeof(Element) * 8) {
             destElem = destElem;
-        else
+        } else {
             destElem = (srcElem1 >> imm) |
                 (destElem & ~mask(sizeof(Element) * 8 - imm));
+        }
     '''
     twoRegShiftInst("vsri", "NVsriD", "SimdShiftOp", unsignedTypes, 2, vsriCode, True)
     twoRegShiftInst("vsri", "NVsriQ", "SimdShiftOp", unsignedTypes, 4, vsriCode, True)
 
     vshlCode = '''
-        if (imm >= sizeof(Element) * 8)
+        if (imm >= sizeof(Element) * 8) {
             destElem = (srcElem1 << (sizeof(Element) * 8 - 1)) << 1;
-        else
+        } else {
             destElem = srcElem1 << imm;
+        }
     '''
     twoRegShiftInst("vshl", "NVshlD", "SimdShiftOp", unsignedTypes, 2, vshlCode)
     twoRegShiftInst("vshl", "NVshlQ", "SimdShiftOp", unsignedTypes, 4, vshlCode)
 
     vsliCode = '''
-        if (imm >= sizeof(Element) * 8)
+        if (imm >= sizeof(Element) * 8) {
             destElem = destElem;
-        else
+        } else {
             destElem = (srcElem1 << imm) | (destElem & mask(imm));
+        }
     '''
     twoRegShiftInst("vsli", "NVsliD", "SimdShiftOp", unsignedTypes, 2, vsliCode, True)
     twoRegShiftInst("vsli", "NVsliQ", "SimdShiftOp", unsignedTypes, 4, vsliCode, True)

src/mem/ruby/system/DMASequencer.cc

@@ -45,7 +45,7 @@ DMASequencer::init()
 {
     RubyPort::init();
     m_is_busy = false;
-    m_data_block_mask = ~ (~0 << RubySystem::getBlockSizeBits());
+    m_data_block_mask = mask(RubySystem::getBlockSizeBits());
 
     for (const auto &s_port : slave_ports)
         s_port->sendRangeChange();