firmware: qcom: scm: fix compilation error when disabled

This fixes the case when CONFIG_QCOM_SCM is not enabled, and linux/errno.h
has not been included previously.
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

include/linux/qcom_scm.h

@@ -67,6 +67,9 @@ extern int qcom_scm_iommu_secure_ptbl_init(u64 addr, u32 size, u32 spare);
 extern int qcom_scm_io_readl(phys_addr_t addr, unsigned int *val);
 extern int qcom_scm_io_writel(phys_addr_t addr, unsigned int val);
 #else
+
+#include <linux/errno.h>
+
 static inline
 int qcom_scm_set_cold_boot_addr(void *entry, const cpumask_t *cpus)
 {