Update to v5.5 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.5

Test: Boots on walleye.
Test: Ran bionic-unit-tests on walleye.
Test: Boots on cuttlefish.
Test: Ran bionic-unit-tests on cuttlefish.
Change-Id: I57387d3c31e0ba5ad125ffe291cecf365c7b374e
Merged-In: I57387d3c31e0ba5ad125ffe291cecf365c7b374e
diff --git a/libc/kernel/uapi/linux/pci_regs.h b/libc/kernel/uapi/linux/pci_regs.h
index a3db220..5501de0 100644
--- a/libc/kernel/uapi/linux/pci_regs.h
+++ b/libc/kernel/uapi/linux/pci_regs.h
@@ -21,6 +21,7 @@
 #define PCI_CFG_SPACE_SIZE 256
 #define PCI_CFG_SPACE_EXP_SIZE 4096
 #define PCI_STD_HEADER_SIZEOF 64
+#define PCI_STD_NUM_BARS 6
 #define PCI_VENDOR_ID 0x00
 #define PCI_DEVICE_ID 0x02
 #define PCI_COMMAND 0x04
@@ -574,6 +575,8 @@
 #define PCI_EXP_LNKCTL2_TLS_8_0GT 0x0003
 #define PCI_EXP_LNKCTL2_TLS_16_0GT 0x0004
 #define PCI_EXP_LNKCTL2_TLS_32_0GT 0x0005
+#define PCI_EXP_LNKCTL2_ENTER_COMP 0x0010
+#define PCI_EXP_LNKCTL2_TX_MARGIN 0x0380
 #define PCI_EXP_LNKSTA2 50
 #define PCI_CAP_EXP_ENDPOINT_SIZEOF_V2 52
 #define PCI_EXP_SLTCAP2 52