libxc/pm: Fix NULL pointer checks.

Discovered by Coverity,
CIDs 1054968 1054969 1054970 1054971 1054972 1054973 10549704

This was broken by c/s 5cc436c1d2 which did a blanket change of 'int
xc_handle' -> 'xc_interface *xch'.  The types got updated, but error
conditions were left as-were.  (I suspect some sed was involved originally)

Also while playing around in this area, fix up some of the bracketing style to
match the Xen coding style.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>

tools/libxc/xc_pm.c

@@ -285,7 +285,7 @@ int xc_set_cpufreq_gov(xc_interface *xch, int cpuid, char *govname)
     DECLARE_SYSCTL;
     char *scaling_governor = sysctl.u.pm_op.u.set_gov.scaling_governor;
 
-    if ( (xch < 0) || (!govname) )
+    if ( !xch || !govname )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;
@@ -302,7 +302,7 @@ int xc_set_cpufreq_para(xc_interface *xch, int cpuid,
 {
     DECLARE_SYSCTL;
 
-    if ( xch < 0 )
+    if ( !xch )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;
@@ -319,7 +319,7 @@ int xc_get_cpufreq_avgfreq(xc_interface *xch, int cpuid, int *avg_freq)
     int ret = 0;
     DECLARE_SYSCTL;
 
-    if ( (xch < 0) || (!avg_freq) )
+    if ( !xch || !avg_freq )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;
@@ -384,7 +384,7 @@ int xc_get_cpuidle_max_cstate(xc_interface *xch, uint32_t *value)
     int rc;
     DECLARE_SYSCTL;
 
-    if ( xch < 0 || !value )
+    if ( !xch || !value )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;
@@ -401,7 +401,7 @@ int xc_set_cpuidle_max_cstate(xc_interface *xch, uint32_t value)
 {
     DECLARE_SYSCTL;
 
-    if ( xch < 0 )
+    if ( !xch )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;
@@ -416,7 +416,7 @@ int xc_enable_turbo(xc_interface *xch, int cpuid)
 {
     DECLARE_SYSCTL;
 
-    if ( xch < 0 )
+    if ( !xch )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;
@@ -429,7 +429,7 @@ int xc_disable_turbo(xc_interface *xch, int cpuid)
 {
     DECLARE_SYSCTL;
 
-    if ( xch < 0 )
+    if ( !xch )
         return -EINVAL;
 
     sysctl.cmd = XEN_SYSCTL_pm_op;