Update to android-mainline kernel headers v5.4.

Update generate_uapi_headers.sh to checkout the android mainline
kernel. Also, add a small modification to look for the kernel directory
in common not linux-stable.

Remove deprecated android headers from android/uapi/linux. Also,
remove f_accessory.h since it's in the android mainline kernel.

Test: Builds and runs on walleye.
Change-Id: Ia371305e19f56e6bcc2db6d5b4d299819f07ffc6
diff --git a/libc/kernel/uapi/linux/pci_regs.h b/libc/kernel/uapi/linux/pci_regs.h
index bd4d98f..a3db220 100644
--- a/libc/kernel/uapi/linux/pci_regs.h
+++ b/libc/kernel/uapi/linux/pci_regs.h
@@ -500,6 +500,7 @@
 #define PCI_EXP_SLTCTL_CCIE 0x0010
 #define PCI_EXP_SLTCTL_HPIE 0x0020
 #define PCI_EXP_SLTCTL_AIC 0x00c0
+#define PCI_EXP_SLTCTL_ATTN_IND_SHIFT 6
 #define PCI_EXP_SLTCTL_ATTN_IND_ON 0x0040
 #define PCI_EXP_SLTCTL_ATTN_IND_BLINK 0x0080
 #define PCI_EXP_SLTCTL_ATTN_IND_OFF 0x00c0
@@ -611,7 +612,9 @@
 #define PCI_EXT_CAP_ID_DPC 0x1D
 #define PCI_EXT_CAP_ID_L1SS 0x1E
 #define PCI_EXT_CAP_ID_PTM 0x1F
-#define PCI_EXT_CAP_ID_MAX PCI_EXT_CAP_ID_PTM
+#define PCI_EXT_CAP_ID_DLF 0x25
+#define PCI_EXT_CAP_ID_PL_16GT 0x26
+#define PCI_EXT_CAP_ID_MAX PCI_EXT_CAP_ID_PL_16GT
 #define PCI_EXT_CAP_DSN_SIZEOF 12
 #define PCI_EXT_CAP_MCAST_ENDPOINT_SIZEOF 40
 #define PCI_ERR_UNCOR_STATUS 4
@@ -896,4 +899,10 @@
 #define PCI_L1SS_CTL1_LTR_L12_TH_VALUE 0x03ff0000
 #define PCI_L1SS_CTL1_LTR_L12_TH_SCALE 0xe0000000
 #define PCI_L1SS_CTL2 0x0c
+#define PCI_DLF_CAP 0x04
+#define PCI_DLF_EXCHANGE_ENABLE 0x80000000
+#define PCI_PL_16GT_LE_CTRL 0x20
+#define PCI_PL_16GT_LE_CTRL_DSP_TX_PRESET_MASK 0x0000000F
+#define PCI_PL_16GT_LE_CTRL_USP_TX_PRESET_MASK 0x000000F0
+#define PCI_PL_16GT_LE_CTRL_USP_TX_PRESET_SHIFT 4
 #endif