target/ppc: init 'lpcr' in kvmppc_enable_cap_large_decr()

'lpcr' is used as an input of kvm_get_one_reg(). Valgrind doesn't
understand that and it returns warnings as such for this function:

==55240== Thread 1:
==55240== Conditional jump or move depends on uninitialised value(s)
==55240==    at 0xB011E4: kvmppc_enable_cap_large_decr (kvm.c:2546)
==55240==    by 0x92F28F: cap_large_decr_cpu_apply (spapr_caps.c:523)
==55240==    by 0x930C37: spapr_caps_cpu_apply (spapr_caps.c:921)
==55240==    by 0x955D3B: spapr_reset_vcpu (spapr_cpu_core.c:73)
==55240==    by 0x95612B: spapr_cpu_core_reset (spapr_cpu_core.c:209)
==55240==    by 0x95619B: spapr_cpu_core_reset_handler (spapr_cpu_core.c:218)
==55240==    by 0xD3605F: qemu_devices_reset (reset.c:69)
==55240==    by 0x92112B: spapr_machine_reset (spapr.c:1641)
==55240==    by 0x4FBD63: qemu_system_reset (runstate.c:444)
==55240==    by 0x62812B: qdev_machine_creation_done (machine.c:1247)
==55240==    by 0x5064C3: qemu_machine_creation_done (vl.c:2725)
==55240==    by 0x5065DF: qmp_x_exit_preconfig (vl.c:2748)
==55240==  Uninitialised value was created by a stack allocation
==55240==    at 0xB01158: kvmppc_enable_cap_large_decr (kvm.c:2540)

Init 'lpcr' to avoid this warning.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20220331001717.616938-3-danielhb413@gmail.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

target/ppc/kvm.c

@@ -2537,7 +2537,7 @@ int kvmppc_get_cap_large_decr(void)
 int kvmppc_enable_cap_large_decr(PowerPCCPU *cpu, int enable)
 {
     CPUState *cs = CPU(cpu);
-    uint64_t lpcr;
+    uint64_t lpcr = 0;
 
     kvm_get_one_reg(cs, KVM_REG_PPC_LPCR_64, &lpcr);
     /* Do we need to modify the LPCR? */