x86/vt-d: Fix incorrect bit operations in setting values

x86/vt-d: Fix incorrect bit operations in setting values

The function context_set_address_root() and set_root_value are setting new
address in a wrong way, and this patch is trying to fix this problem.

According to Intel Vt-d specs(Feb 2011, Revision 1.3), Chapter 9.1 and 9.2,
field ctp in root entry is using bits 12:63, field asr in context entry is
using bits 12:63.

To set these fields, the following functions are used:
static inline void context_set_address_root(struct context_entry *context,
        unsigned long value);
and
static inline void set_root_value(struct root_entry *root, unsigned long value)

But they are using an invalid method to set these fields, in current code, only
a '|' operator is used to set it. This will not set the asr to the expected
value if it has an old value.

For example:
Before calling this function,
	context->lo = 0x3456789012111;
	value = 0x123456789abcef12;

After we call context_set_address_root(context, value), expected result is
	context->lo == 0x123456789abce111;

But the actual result is:
	context->lo == 0x1237577f9bbde111;

So we need to clear bits 12:63 before setting the new value, this will fix
this problem.

Signed-off-by: Li, Zhen-Hua <zhen-hual@hp.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>